Method and apparatus for obtaining blood for diagnostic tests

ABSTRACT

Method and apparatus for obtaining a sample of blood from a patient for subsequent diagnostic tests, e.g., glucose monitoring. In one aspect of the invention, the method comprises the steps of: 
     (a) forming an unobstructed opening in the area of the skin from which the sample of blood is to be extracted; and 
     (b) extracting the sample of blood from the unobstructed opening in the skin, with the aid of a vacuum and a stretching of the skin. 
     In another aspect of the invention, an apparatus for carrying out the method described previously is provided. The apparatus comprises: 
     (a) a device for forming an unobstructed opening in an area of skin from which said sample is to be extracted, preferably a lancing assembly; and 
     (b) a vacuum pump. 
     Preferably, the apparatus also includes a housing. 
     In a further aspect of the invention, a pneumatic lancing assembly is provided. The pneumatic lancing assembly uses differential gas pressure to thrust a lancet into skin tissue. This lancing assembly effectively utilizes low-pressure gas, which is preferably provided by the aforementioned vacuum pump, and high-pressure gas, which is preferably provided by ambient air surrounding the apparatus, to thrust the lancet, puncture the skin, and then retract the lancet from the skin to produce an unobstructed opening to allow access to biological fluid.

This application is a continuation-in-part of U.S. Ser. No. 08/759,698,filed Dec. 6, 1996 and a continuation-in-part of U.S. ProvisionalApplication No. 60/036,395, filed Jan. 24, 1997.

CROSS REFERENCES TO COPENDING APPLICATIONS

This application relates to three patent applications, METHOD ANDAPPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's DocketNo. 6005.US.P2, METHOD AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTICTESTS, Attorney's Docket No. 6005.US.P3, METHOD AND APPARATUS FOROBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US.P4,filed on evendate herewith. The specifications, drawings, and claims ofthese applications are incorporated herein by reference. All of theforegoing applications are commonly owned by the assignee of thisinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for obtaining samplesof blood for diagnostic purposes.

2. Discussion of the Art

The prevalence of diabetes has been increasing markedly in the world. Atthis time, diagnosed diabetics represented about 3% of the population ofthe United States. It is believed that the total actual number ofdiabetics in the United States is over 16,000,000. Diabetes can lead tonumerous complications, such as, for example, retinopathy, nephropathy,and neuropathy.

The most important factor for reducing diabetes-associated complicationsis the maintenance of an appropriate level of glucose in the bloodstream. The maintenance of the appropriate level of glucose in the bloodstream may prevent and even reverse many of the effects of diabetes.

Glucose monitoring devices of the prior art have operated on theprinciple of taking blood from an individual by a variety of methods,such as by needle or lancet. An individual then coats a paper stripcarrying chemistry with the blood, and finally insert the blood-coatedstrip into a blood glucose meter for measurement of glucoseconcentration by determination of change in reflectance.

The medical apparatus of the prior art for monitoring the level ofglucose in the blood stream required that an individual have separatelyavailable a needle or lancet for extracting blood from the individual,strips carrying blood chemistry for creating a chemical reaction withrespect to the glucose in the blood stream and changing color, and ablood glucose meter for reading the change in color indicating the levelof glucose in the blood stream. The level of blood glucose, whenmeasured by a glucose meter, is read from a strip carrying the bloodchemistry through the well-known process of reading reflectometers 15for glucose oxidation.

Generally lancets comprise a blade and a pressable end opposed thereto,with the blade having an acute end capable of being thrust into skin ofa human. By striking the pressable portion, the acute end of the bladewill pierce the skin, for example, of the finger. The finger lancet isprimarily used to obtain small volumes of blood, i.e., less than 1 mL.Diabetics use the finger lancet to obtain volumes of blood less than 25μL for analysis for glucose. A small amount of blood for the blood testwill ooze out of the skin. There are many small blood vessels in eachfinger so that a finger can be squeezed to cause a larger drop of bloodto ooze. The finger is one of the most sensitive parts of the body;accordingly, the finger lancet leads to even more pain than what wouldbe experienced by extracting blood via lancet at a different body site.The finger lancet presents another problem because of the limited areaavailable on the fingers for lancing. Because it is recommended thatdiabetics monitor their blood glucose levels four to six times per day,the limited area on the fingers calls for repeated lancing of areas thatare already sore. Because fingers are sensitive to pain, it is a recenttendency that the arm is subjected to blood sampling. See, for example,U.S. Pat. No. 4,653,513. The device of U.S. Pat. No. 4,653,513 comprisesa cylindrical housing and a lancet support, which has a gasket orflexible portion slidably accommodated in the housing. Springs willretract the lancet support to thereby reduce air pressure in the housingso that it sucks a blood sample, automatically and immediately after alancet pierces the skin. See also U.S. Pat. No. 5,320,607, whichdiscloses a device comprising a sealed vacuum chamber in a state ofpreexisting reduced pressure, a support member for the sealed vacuumchamber, the support member defining a suction portion adjacent thesealed vacuum chamber, the suction portion, in cooperation with thesealed vacuum chamber, exposing an area of the skin of a patient to areduced pressure state when the device is actuated, and means arrangedwithin the suction portion for slightly rupturing a portion of the areaof skin of the patient exposed to the reduced pressure state.

Because the blood volume requirements for a standard glucose test stripis typically 3 μL or more, an area of the body that can generate thatmuch blood from a lancet wound must be used. It is believed, however,that improvements in glucose test strip technology will reduce thevolume of blood needed to 1 to 3 μL. Because the finger is well suppliedwith blood and the amount of blood can be increased by squeezing thefinger after lancing, the finger is the currently preferred body sitefor lancing, even though lancing of the finger is painful.

A less painful technique for obtaining body fluids could be found if areliable method were found for lancing a body part that is lesssensitive to pain than the finger and obtaining a useful amount of bloodfrom that body part. A body part such as the forearm is much lesssensitive to pain than the finger, but the amount of blood resultingfrom the lancing procedure is generally of an inadequate volume for usewith current detection technology. Ways of increasing blood flow to thefinger are common knowledge. The recommendation is made to diabetics torun their finger under hot water prior to lancing to improve the bloodflow in the finger and the amount of blood collected from the finger.Running hot water over a body part to improve blood flow is impracticalfor areas such as the forearm or thigh. The availability of hot water isalso a concern.

It would be desirable to develop a technique and apparatus for obtainingblood for diagnostic purposes in a painless, reliable manner.

Conventional lancing devices, such as those described in U.S. Pat. Nos.Re. 32,922, 4,203,446, 4,990,154, and 5,487,748, accept commerciallyavailable, disposable lancets. Most conventional lancing devices are notintegrated with a diagnostic instrument. A conventional lancingmechanism typically consists of a housing, a guided shaft having alancet holder at one end, a main spring (usually helical) that suppliesthe mechanical energy to axially accelerate the shaft, and a returnspring that partially retracts the shaft after lancing has occurred. Theuser must first insert a lancet into the holder, then manually slide theshaft until the main spring is compressed and the shaft is locked intoits "cocked" position, then place the device against the skin, thenpress a trigger, which releases the shaft, thereby driving the lancetinto the skin. The lancet is quickly retracted from the skin by theforce of the return spring.

Conventional lancing devices would have several disadvantages for anapparatus that combines the processes of lancing, fluid collecting, andanalyte sensing into one automated instrument. The first disadvantage isthe necessity of manually cocking the lancing mechanism prior to eachuse. Manual cocking is inconvenient for the user and generally adverselyaffects the automated characteristics of an integrated instrument.Manual cocking also prohibits rapid, sequential lancing of the targetskin. Sequential lancing could increase the volume of biological fluidcollected. The second disadvantage is that the mechanical trigger can beaccidentally pressed by the user if the device is mishandled. Accidentaltriggering of the lancet could injure the user and cause technicalproblems within an automated lancing system. The user would be furtherinconvenienced by having to re-cock the mechanism after accidentaltriggering. The third disadvantage is that the conventional returnspring is generally not able to completely retract the lancet, due tothe opposing force of the main spring. Partial retraction may subjectthe user to accidental punctures when handling the instrument before orafter use, particularly when the lancet is located near other disposablecomponents, such as fluid sample collection strips.

It would therefore be desirable to provide a lancing device thateliminates one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

This invention provides a method and apparatus for extracting a sampleof blood from a patient for subsequent diagnostic tests, e.g., glucosemonitoring. In one aspect of the invention, the method comprises thesteps of:

(a) forming an unobstructed opening in the area of the skin from whichthe sample of blood is to be extracted; and

(b) extracting the sample of blood from the unobstructed opening in theskin, with the aid of vacuum and stretching of the skin.

In a preferred embodiment of the method, step (a) is preceded by thestep of increasing the availability of blood in the portion of the skinfrom which the sample is to be extracted. In this preferred embodiment,the availability of blood in the portion of the skin from which thesample is to be extracted can be increased by means of a vacuum, whichis applied to the surface of the skin in the vicinity of the openingprior to forming the opening in the skin. The vacuum causes the portionof the skin in the vicinity of the blood extraction site to becomeengorged with blood. The vacuum also causes the portion of the skin inthe vicinity of the blood extraction site to become stretched. Anopening in this stretched portion of skin can be formed with a cuttingor puncturing device, e.g., a lancet, or other device capable of formingan opening in the skin, e.g., a laser or a fluid jet. If a cutting orpuncturing device is used to form the opening, it must be retracted fromthe opening prior to the step of extracting the sample of blood from theopening. This retraction will allow the unrestricted flow of bloodthrough the opening. After the opening is formed, a vacuum is used toaid in extracting the sample of blood from the opening in the skin. Thesample can be analyzed from the drops of blood that collect on thesurface of the skin at the site of the opening by applying the blooddirectly to a glucose detector. It is preferred, however, that thesample be collected in such a manner, e.g., via a capillary tube, thatit can be analyzed by conventional diagnostic devices, such as, forexample, a biosensor. In another preferred embodiment, the sample can becollected in a collection zone that is integrated with a conventionaldiagnostic device, e.g., a biosensor.

In an alternative of the aforementioned preferred embodiment, theavailability of blood in the area of the skin from which the sample isto be extracted can be increased by means of applying thermal energy tothat area of skin. The thermal energy causes the blood in that area ofthe skin to flow more rapidly, thereby allowing more blood to becollected per given unit of time. In this alternative embodiment, steps(a) and (b) can be carried out in the same manner as they were carriedout in the aforementioned preferred embodiment.

In another aspect of the invention, an apparatus for collecting a sampleof body fluid for analysis in a diagnostic test, e.g., blood, isprovided. In a preferred embodiment, the apparatus comprises:

(a) a housing;

(b) a device for forming an unobstructed opening in an area of skin fromwhich said sample is to be extracted, preferably a lancing assembly; and

(c) a vacuum pump.

It is also possible to dispense with the housing. However, the housingis preferred for the convenience of the patient and the protection ofthe components.

The vacuum pump requires a source of power. If the apparatus includes ahousing, the source of power can be disposed within the housing.Alternatively, the source of power can be external to the housing.

The preferred device for forming an unobstructed opening in the area ofthe skin from which the sample of blood is to be extracted is a lancingassembly, which comprises a lancet for forming an opening in the skin.Alternatively, the unobstructed opening in the skin can be formed by alaser or a fluid jet.

The vacuum pump can serve the dual purposes of (1) stretching the skinand (2) enhancing the extraction of the sample of blood from theunobstructed opening in the skin. Preferably, the vacuum pump can servethe triple purposes of (1) stretching the skin, (2) increasing theavailability of blood to the area of the skin from which the sample isto be extracted, and (3) enhancing the extraction of the sample of bloodfrom the unobstructed opening in the skin. Preferably, the housingfurther contains electronics having programmed instructions to switchthe vacuum pump on and off to maintain the desired level of vacuum.

The apparatus preferably contains valves, such as, for example, solenoidvalves, for triggering the lancet of the lancing assembly and releasingthe vacuum at the conclusion of the blood extraction procedure. Theapparatus can optionally contain a heating element to increase theavailability of blood to the area of the skin from which the sample isto be extracted. The apparatus can also contain a glucose detectorintegrated with the apparatus, e.g., a biosensor, to analyze the sampleof blood collected by the apparatus.

In another aspect of this invention, a lancing assembly that usesdifferential gas pressure to thrust a lancet into skin tissue has beendeveloped. This lancing assembly effectively utilizes low-pressure gas,which is preferably provided by the aforementioned vacuum pump, andhigh-pressure gas, which is preferably provided by ambient airsurrounding the apparatus, to thrust the lancet, puncture the skin, andthen retract the lancet from the skin to produce an unobstructed openingto allow access to biological fluid. The lancing assembly eliminates theneed to manually force the lancing mechanism into a latched, or"cocked", position prior to each use, and also eliminates the need for amechanical trigger to release the latch to allow the lancet to be thrustinto the skin. Elimination of the requirement to manually cock thelancing mechanism allows the lancing assembly to be controlledexclusively by electronic means. Such means of control is desirable whenused in conjunction with an automated instrument, or when a continuousseries of lancing steps is desired.

The lancing assembly that utilizes differential gas pressure comprises:

(a) a holder for holding a lancet assembly;

(b) a means for providing sufficient force to cause the holder to bemaintained in a position whereby a lancet assembly in the holder wouldbe positioned away from the skin of the patient; and

(c) a means for allowing a gas to provide sufficient force to overcomethe force provided by the holder maintaining means, whereby the gascauses the holder to be moved to a position whereby a lancet in theholder would be able to pierce the skin of the patient.

In one embodiment, the lancing assembly comprises a housing, a lancetholder, a piston for moving the lancet holder, a bore in which thepiston moves toward and away from the target skin tissue, a means forbiasing the piston, e.g., a return spring or a bellows, away from thetarget skin tissue, and a cap. The housing has a manifold into which athree-way valve can be fitted. The three-way valve selectively allowshigh-pressure air from a source external to the housing to pass throughan inlet port to a bore port, thereby causing the level of pressure inthe bore to increase. The air pressure in the bore thrusts the pistontoward the target skin tissue while simultaneously compressing thepiston biasing means. The piston is halted by the cap or by a structurein the instrument designed to limit the penetration depth of the lancetin the skin. The three-way valve then directs the air in the bore toflow out through an exit port to a source of low-pressure air, e.g., anevacuated air cavity in the apparatus, thereby causing the level ofpressure in the bore to decrease, and consequently allowing the pistonbiasing means to force the piston back to its pre-thrust position in thebore.

The method and apparatus of this invention provide several advantagesover the methods and apparatus of the prior art. First, a sufficientamount of blood can be extracted from parts of the body, other than thefinger, for conducting glucose monitoring tests. Second, by renderingother parts of the body suitable for extracting blood, the use of apainful finger lance can be avoided. Third, by increasing theavailability of blood at the site where the blood is to be extracted,the period of time required for extracting the sample can be reduced.Because of these advantages, the diabetic patient is more likely tomonitor glucose levels in the blood at the intervals prescribed by hisdoctor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the components of a preferred embodiment of theapparatus of this invention. In this Figure, the cover of the housing isremoved.

FIG. 2 is a schematic diagram illustrating how a vacuum causes a portionof the skin to become stretched prior to the formation of an opening inthe skin from which the sample of blood is extracted. FIG. 2 alsoillustrates the spatial relationship between the nosepiece. of lancingassembly and a glucose detector, e.g., a biosensor.

FIG. 3 is a block diagram illustrating the electronics of the preferredembodiment.

FIG. 4 is a schematic diagram illustrating an alternative seal for thevacuum of the device of the present invention.

FIG. 5 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 6 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 7 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 8 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 9 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 10 is a perspective view of an embodiment of the apparatus of thisinvention. In this figure, the housing of the apparatus is open.

FIG. 11 is an elevational view, in cross section, of one embodiment ofthe lancing assembly of this invention in assembled configuration.

FIG. 12 is an exploded view, in cross section, of the lancing assemblyof FIG. 11.

FIG. 13 is a schematic diagram illustrating the positioning of thecomponents of the lancing assembly of this invention. In this figure,the lancet assembly has not yet been inserted into the lancet holder andthe valve has not yet been inserted into the valve manifold.

FIG. 14 is a schematic diagram illustrating the positioning of thecomponents of the lancing assembly of this invention. In this figure,the lancet has been inserted into the lancet holder and the valve hasbeen inserted into the valve manifold.

FIGS. 15A, 15B, and 15C are schematic diagrams illustrating the lancingassembly of this invention in the pre-lancing position, the lancingposition, and the post-lancing position, respectively.

FIG. 16 is an elevational view, in cross section, of another embodimentof the lancing assembly of this invention in assembled configuration.

FIG. 17 is an exploded view, in cross section, of the lancing assemblyof FIG. 16.

FIG. 18 is an elevational view, in cross section, of another embodimentof the lancing assembly of this invention in assembled configuration.

FIG. 19 is an exploded view, in cross section, of the lancing assemblyof FIG. 18.

FIG. 20 is an elevational view, in cross section, of the lancingassembly of this invention installed in an embodiment of an apparatus ofthis invention.

DETAILED DESCRIPTION

The embodiments of this invention require the following steps to carryout the function of obtaining a sample of blood for carrying out adiagnostic test, e.g., glucose monitoring:

(a) forming an unobstructed opening in the area of the skin from whichthe sample of blood is to be extracted; and

(b) extracting the sample of blood from the unobstructed opening in theskin, with the aid of a vacuum and a stretching of the skin.

The step of forming an unobstructed opening in the area of the skin fromwhich the sample of blood is to be extracted is carried out by apiercing device or some other type of device capable of forming anunobstructed opening in the skin. Piercing devices suitable for thisinvention include, but are not limited to, mechanical lancingassemblies. Other type of device capable of forming an unobstructedopening in the skin include, but are not limited to, lasers and fluidjets. Other types of devices capable of forming an unobstructed openingin the skin can be used, and this disclosure should not be construed soas to be limited to the devices listed. Mechanical lancing assembliesare well-known in the art. These assemblies comprise include standardsteel lancets, serrated devices, and multiple tip devices. The lancetscan be made from metal or plastic. Multiple tip devices provideredundancy, which can reduce the number of failures and increase thevolume of blood extracted.

Lasers suitable for forming an unobstructed opening in the skin to drawblood are also well-known in the art. See for example, U.S. Pat. Nos.4,775,361, 5,165,418, 5,374,556, International Publication Number WO94/09713, and Lane et al. (1984) IBM Research Report--"Ultraviolet-LaserAblation of Skin", all of which are incorporated herein by reference.Lasers that are suitable for forming an unobstructed opening in the skinthe skin include Er:YAG, Nd:YAG, and semiconductor lasers.

Fluid jets suitable for forming an unobstructed opening in the skinemploy a high pressure jet of fluid, preferably a saline solution, topenetrate the skin.

Regardless of what type of device is utilized to form an unobstructedopening in the skin, the opening formed by the device must beunobstructed. As used herein, the term "unobstructed" means free fromclogging, hampering, blocking, or closing up by an obstacle. Morespecifically, the expressions "unobstructed opening in the area of theskin from which the sample is to be extracted", "unobstructed opening inthe skin", and the like are intended to mean that the portion of theopening below the surface of the skin is free from any foreign objectthat would clog, hamper, block, or close up the opening, such as, forexample, a needle of any type. For example, if a lancet is used to formthe opening, it must be retracted from the opening prior to thecommencement of the extraction of blood. Because lasers and fluid jetsdo not require contact with the skin to form openings in the skin, thesetypes of devices typically provide unobstructed openings. However, theseexpressions are not intended to include foreign objects at the surfaceof the skin or above the surface of the skin, such as, for example, aglucose monitor. This feature, i.e., the unobstructed opening, can becontrasted with the opening used in the method and apparatus describedin U.S. Pat. No. 5,320,607, in which the piercing and cutting meansremains in the skin during the duration of the period of bloodextraction. By leaving the opening unobstructed, blood can be extractedmuch more rapidly from the opening than it would be extracted if thepiercing and cutting means were allowed to remain in the opening. Inaddition, the requirement of an unobstructed opening exposes the body toa foreign object either not at all or for only a very short period oftime, which is welcomed by the patient.

The step of extracting the sample of blood from the opening in the skinis carried out by a combination of extraction enhancing elements.Extraction enhancing elements suitable for use in this inventioninclude, but are not limited to, vacuum, skin stretching elements, andheating elements. It has been discovered that when these elements areused in combination, the volume of blood extracted is greatly increased,particularly when a vacuum is applied in combination with skinstretching. In this combination, the vacuum not only causes the blood tobe rapidly removed from the unobstructed opening by suction, it alsocauses a portion of the skin in the vicinity of the opening to bestretched. Stretching of the skin can be effected by other means, suchas mechanical means or adhesives. Mechanical means include devices forpinching or pulling the skin; adhesives bring about stretching of theskin by means of pulling. It is preferred to use a vacuum to effectstretching of the skin. Like a vacuum, a heating element operates moreeffectively in combination with other techniques, e.g., stretching ofthe skin.

In the preferred embodiment of this invention, step (a), the step offorming the unobstructed opening, is preceded by the step of increasingthe availability of blood at the area of the skin from which the sampleis to be extracted. The availability of blood at a given area of theskin can be increased by at least two methods. In one method, a vacuumcan be used to cause blood flowing through blood vessels to pool in thearea of the skin where the vacuum is applied. In another method, heatcan be used to cause blood flowing through blood vessels to flow morerapidly in the area of the skin where heat is applied, thereby allowinga greater quantity of blood to be extracted from the blood extractionsite per unit of time. Although the step of increasing the availabilityof blood in the vicinity of the blood extraction site is not required,the employment of this step can result in a greater volume of bloodextracted. Elements for increasing the availability of blood at a bloodextraction site that are suitable for use in this invention include, butare not limited to, vacuum, localized heating element, skin stretchingelement, and chemicals. As stated previously, applying a vacuum to thearea of the skin from which blood is to be extracted can increase bloodavailability under and within the skin at the application site. Thevacuum can also be used to stretch the skin upwardly into a chamber,thereby increasing pooling of blood under and within the skin. Thiscombination of vacuum and skin stretching can be an extension of thecombination used to extract blood from the opening in the skin, aspreviously described. It is well known that heat can increase perfusionon the large scale of a limb or a finger. Chemical means, such ashistamine, can be used to cause a physiological response to increaseperfusion under and within the skin.

In the preferred embodiments of the invention, the extracted blood isalso collected. The step of collecting the sample of blood can becarried out in a variety of ways. For example, the blood can becollected in capillary tubes or absorbent paper. Alternatively, theblood can be allowed to remain in the lancet assembly, from which it canused directly in a diagnostic test. Most preferably, the sample of bloodis collected on the application zone of a glucose detector, from whereit can be used directly to provide an indication of the concentration ofglucose in the blood. Regardless of the manner in which the blood sampleis collected, the sample can be analyzed at a time later than the timeof collection or at a location remote from the location of collection orboth.

A preferred embodiment of the invention will now be described in detail.Blood extraction device 10 comprises a housing 12. Disposed within thehousing 12 are a vacuum pump 14, a lancing assembly 16, a battery 18,and electronics 20. A switch 22 is provided to activate electronics 20.

The housing 12 is preferably made from a plastic material. It ispreferably of sufficient size to contain all of the components that arerequired for forming an unobstructed opening in the area of the skinfrom which the sample of blood is to be extracted, extracting the sampleof blood from the unobstructed opening in the skin, preferably with theaid of a vacuum and a stretching of the skin, and collecting theextracted sample in an amount sufficient to carry out a diagnostic test.Methods of preparing the housing 12 are well-known to one of ordinaryskill in the art. As stated previously, the housing 12 is not required,but is preferred for the convenience of the patient and the protectionof the components.

The vacuum pump 14 must be capable of providing a vacuum that willprovide sufficient suction to stretch the portion of the skin in theregion from which the sample of blood is to be extracted. Typically, theportion of stretched skin is raised a distance of 1 to 10 mm, preferably3 to 5 mm, from the plane of the body part of which it is a portion. Asthe suction provided by the vacuum pump 14 is stretching the appropriateportion of skin, the suction provided by the vacuum pump 14 also causesthe stretched portion to become engorged with blood. The level ofsuction provided must be sufficient to cause a relatively large volumeof blood to become engorged at the point that the vacuum is applied. Thevacuum pump 14 must also be capable of providing sufficient suction toextract blood from the opening in the skin at a rate sufficient toextract at least 1 μL of blood within a period of five minutes. A vacuumpump 14 that is suitable for the device of this invention can be adiaphragm pump, a piston pump, a rotary vane pump, or any other pumpthat will perform the required functions set forth previously.Typically, the vacuum pump 14 employs a self-contained permanent magnetDC motor. Vacuum pumps that are suitable for this invention arewell-known to those of ordinary skill in the art and are commerciallyavailable. A vacuum pump suitable for use in the present invention isavailable from T-Squared Manufacturing Company, Nutley, N.J., and hasthe part number T2-03.08.004.

The vacuum pump 14 is preferably capable of providing a pressure of downto about -14.7 psig, and is more preferably operated at from about -3.0psig to about -10.0 psig. The area of the skin subjected to vacuumpreferably ranges up to about 50 cm², more preferably from about 0.1 toabout 5.0 cm². The period of vacuum application prior to forming theopening in the skin, i.e., for increasing the availability of blood tothe application site, preferably ranges up to about 5 minutes,preferably from about 1 to about 15 seconds. The period of vacuumapplication subsequent to forming the opening in the skin, i.e., foraiding in the extraction of blood from the unobstructed opening,preferably ranges up to about 5 minutes, preferably from about 1 toabout 60 seconds. The vacuum provided by the vacuum pump 14 can becontinuous or pulsed. A continuous vacuum is preferred for the reasonthat it requires fewer components than does a pulsed vacuum. It ispreferred that the vacuum applied not cause irreversible damage to theskin. It is preferred that the vacuum applied not produce bruises anddiscolorations of the skin that persist for several days. It is alsopreferred that the level of vacuum applied and duration of applicationof vacuum not be so excessive that it causes the dermis to separate fromthe epidermis, which results in the formation of a blister filled withfluid.

The vacuum pump feature offers significant advantages over the methodand apparatus described in U.S. Pat. No. 5,320,607, in which a sealedvacuum chamber in a state of preexisting reduced pressure is used. Theuse of a vacuum pump provides the user with greater control of bloodextraction conditions than does a sealed vacuum chamber in a state ofpreexisting reduced pressure. For example, if the vacuum isinsufficient, energy can be provided to the vacuum pump to bring about ahigher level of vacuum, thereby providing greater suction.

The lancing assembly 16 comprises at least one lancet. Standard lancetscan be used in the lancing assembly of this invention. Narrow gauge (28to 30 gauge) lancets are preferred. Lancets suitable for this inventioncan be made from metal or plastic. Lancets suitable for this inventioncan have single points or multiple points. The depth of penetration ofthe lancet preferably ranges from about 0.4 to about 2.5 mm, morepreferably from about 0.4 to about 1.6 mm. The length of the lancet orlancets preferably ranges from about 1 mm to about 5 mm. The lancingassembly is preferably located so that the user can easily replace usedlancets. The lancet of the lancing assembly 16 can be cocked manually orautomatically, e.g., by means of a vacuum-actuated piston or diaphragm.The lancet of the lancing assembly 16 can be triggered by manually orautomatically, e.g., by means of a vacuum-actuated piston or diaphragm.

Lancing assemblies are well-known in the art. Representative examples oflancing assemblies suitable for this invention are described in U.S.Pat. Nos. Re. 32,922, 4,203,446, 4,990,154, and 5,487,748, all of whichare incorporated herein by reference. A particularly suitable lancingassembly for this invention is described in U.S. Pat. No. Re. 32,922.However, any lancing assembly selected should operate in conjunctionwith the other features of the apparatus of this invention. For example,if a vacuum is employed, the lancing assembly must be designed so that avacuum can be formed and drawn through the assembly. The lancingassembly can be designed to allow automatic cocking and automatictriggering of the lancet.

While conventional lancing assemblies are suitable for use in thisinvention, a lancing assembly that utilizes differential gas pressure tothrust a lancet into skin tissue has been developed for use with thisinvention. As used herein, the expression "differential gas pressure"means the difference in gas pressure between a gas source at a highpressure, e.g., ambient air or pressurized air, and a gas source at alow pressure, e.g., air within a vacuum. In any event, the pressure of agas source at high pressure exceeds the pressure of a gas source at lowpressure.

FIGS. 11, 12, 13, and 14 illustrate an embodiment of a lancing assemblysuitable for use in this invention. In this embodiment, the gas is air.However, it should be noted that other gases, e.g., nitrogen, carbondioxide, can be used in place of air for the gas source at low pressure,the gas source at high pressure, or both. The lancing assembly 60 ofthis embodiment comprises a housing 62, a piston 64 having a lancetholder 66, a lancet assembly 67 comprising a lancet 67a inserted into abody 67b, a piston biasing means 68, which, in this embodiment, is areturn spring, and a cap 70. The housing 62 has a manifold 72 into whicha three-way valve 74 can be fitted. See FIGS. 13 and 14 for manner ofpositioning the three-way valve 74 in the manifold 72. The three-wayvalve 74 selectively allows air from a source external to the housing 62to pass through an inlet port 76 to a bore port 78, thereby causing thelevel of pressure in the bore 80 to increase. The increased pressure inthe bore 80 causes the piston 64 to be thrust toward the target skintissue while simultaneously compressing the return spring 68. The piston64 is halted by the cap 70 or by another structure designed to limit thepenetration depth of the lancet 67a in the skin. Such other structurecan be a glucose detector in the form of a test strip, which will bedescribed later, or a lancet stop, such as that designated by referencenumeral 39 in FIG. 2. The three-way valve 74 then directs the air in thebore 80 to flow out through an exit port 82 to a source of low-pressureair, e.g., an evacuated air cavity in the apparatus, thereby causing thelevel of pressure in the bore 80 to decrease, and consequently allowingthe return spring 68 to force the piston 64 back to its pre-thrustposition in the bore 80.

Proper sizing of the components is needed to satisfy both thedimensional limitations of the apparatus and the performancerequirements of the lancing process, as explained further below. Thelancing assembly of this invention occupies no more space than aconventional spring-powered device and typically requires less distancefor the lancet to travel.

The bore 80, typically cylindrical in shape, is the chamber in whichdifferential air pressure is generated to thrust the piston 64 towardthe target skin tissue. The bore 80 also functions to guide the piston64 toward the target skin tissue, while providing a low-frictionpneumatic seal against o-ring 84. The o-ring 84 is desirable forpreventing high-pressure air from leaking out of the bore 80 during thelancing procedure, because the leakage of high-pressure air willdecrease the level of air pressure in the bore 80, with the result thatthe thrusting speed of the piston 64 would be reduced. The manifold 72is shaped to fit the three-way valve 74, which selectively connects boreport 78 to either inlet port 76 or exit port 82 to direct the flow ofair to or from the bore 80. The exit port 82 is typically plumbed to asource of low-pressure air. The inlet port 76 is typically plumbed to asource of air pressure higher than that of the low-pressure air source.The ports 76, 78, and 82 are positioned to communicate withcorresponding ports of the three-way valve 74, and are preferably sizedto cause less flow resistance than the ports on the three-way valve 74.

The piston 64 is the moving component of the lancing assembly 60. It ispreferably cylindrical in shape, and has a lancet holder 66 and acircumferential gland 83 for a standard o-ring 84. The lancet holder 66is designed to securely mount a disposable lancet assembly 67, which isinserted by the user in the same manner as is used with a conventionallancing device. The lancet assembly 67 comprises a lancet 67a, which isinserted into a molded plastic body 67b. The function of the o-ring 84is to act as a seal to maintain air pressure in the bore 80 duringlancing. The o-ring should cause negligible sliding friction force alongthe bore 80 (negligible compared to pressure forces acting on the piston64 ). The length of the shaft 64a of the piston 64 is chosen to providea desired stroke distance, typically 5 mm to 25 mm. The major dimensionof the top surface 64b of the piston 64, typically 5 mm to 10 mm indiameter for a cylindrically-shaped piston, is chosen to provideadequate surface area for pressure forces to thrust the piston 64 andthe lancet assembly 67.

The return spring 68, typically a metal helical spring, is compressedbetween the piston 64 and the cap 70. The spring 68 forces the piston 64to its maximum depth in the bore 80 when substantially no differentialair pressure exists in the bore 80. This action properly positions thepiston 64 to begin the lancing process. This position of the piston 64is the position in which the piston 64 is furthest away from the targetskin tissue when the apparatus is placed against the target skin tissue.The spring 68 also retracts the lancet assembly 67 in the lancet holder66 away from the target skin tissue at the end of the lancing process.The spring force must be sufficient to overcome the weight of thepiston/lancet system plus the sliding friction of the o-ring 84.

The cap 70 is securely positioned in the housing 62. The cap 70 properlypositions the return spring 68 while providing sufficient radialclearance for the spring 68 to compress freely. The cap 70 has a passage88 through which the lancet holder 66 can move. The cap 70 can alsofunction to help guide the piston 64 toward the target skin tissue.

FIGS. 16 and 17 illustrate another embodiment of the lancing assembly.In these figures, prime reference numerals (i.e., reference numerals60', 62', 64', 64a', 64b', 66', 70', 72', 76', 78', 80', 82', 88')indicate components that are identical or at least substantially similarto components designated by the same reference numerals, but with noprime marking (i.e., reference numerals 60, 62, 64, 66, 70, 72, 76, 78,80, 82, 88 ) in FIGS. 11 and 12. In FIGS. 16 and 17, bellows 89,typically a cylindrical molded elastomer, functions as both thepneumatic seal for bore 80' and the means for biasing piston 64'. Thebellows 89 effectively replaces the o-ring seal 84 and the return spring68 shown in FIGS. 11 and 12. To accommodate the bellows 89, the shaft64a' of the piston 64' must have a radial cross-section dimensionsufficiently smaller than that of the bore 80' to provide sufficientclearance for the bellows 89. A plate 90 fastens and seals the bellows89 to the shaft 64a' of the piston 64', and provides a means of guidingthe piston 64' through the bore 80'. A cap 70' and a housing 62' areshaped to fasten and seal the base of the bellows 89 as shown. Thisembodiment can be used in a manner identical to the embodiment shown inFIGS. 11, 12, 13, 14, 15A, 15B, and 15C. It is clear that the embodimentemploying the bellows 89 offers the potential advantage of reducedsliding friction when compared to the embodiment employing the o-ring84. The bellows does not rub against the surface of the bore in themanner that the o-ring does; therefore, the bellows may result inreduced friction force. The friction force has the undesired effect ofreducing the speed of the piston. It is also clear that the bellowsrequires less dimensional tolerance to be accommodated in the bore 80'than is required to accommodate the o-ring 84 in the bore 80. Thebellows does not need to be precisely fitted into the bore, as does theo-ring. If the bore fits too tightly around the o-ring, then excessivesliding friction may result. It the bore fits too loosely around theo-ring, then excessive air leakage may result. By using the bellows inplace of the o-ring, the manufacturing tolerances in the bore can berelaxed, with the result that manufacturing costs will be reduced andfewer parts will be rejected. The bellows 89 is preferably made of amaterial having sufficient stiffness and sufficient flexibility so thatthe bellows can perform the following functions: (1) act as a seal; (2)resist radial collapse under pressure; (3) allow the lancing assembly toretract to its initial pre-thrust position after the thrusting step; and(4) have its force overcome by differential gas pressure duringoperation.

FIGS. 18 and 19 illustrate another embodiment of the lancing assembly.In these figures, double prime reference numerals (i.e., referencenumerals 60", 62", 64", 64a", 64b", 66", 68", 70", 72", 76", 76", 78",80", 82", 88") indicate components that are identical or at leastsubstantially similar to components designated by the same referencenumerals, but with no prime marking (i.e., reference numerals 60, 62,64, 66, 70, 72, 76, 78, 80, 82, 88) in FIGS. 11 and 12. In FIGS. 18 and19, a diaphragm 84a, typically a molded elastomer, functions as thepneumatic seal for bore 80". The diaphragm 84a, in effect, replaces theo-ring seal 84 shown in FIGS. 11 and 12. The diaphragm 84a is fixed tothe housing 62" and to the shaft 64a" of the piston 64" and can flexwithin the bore 80" when the shaft 64a" of the piston 64" moves axiallyin the bore 80". To accommodate the diaphragm 84a, the shaft 64a" of thepiston 64" must have a radial cross-section dimension sufficientlysmaller than that of the bore 80" to provide sufficient clearance forthe diaphragm 84a. In addition, the housing 62" and the top 62a" of thehousing must have assembly features to which the diaphragm 84a can beinstalled. The assembly features must also effectively seal thediaphragm 84a between the housing 62" and the top 62a" of the housing.The diaphragm 84a is preferably fastened to the shaft 64a" of the piston64" by means of a fastener 83a. This embodiment can be operated in amanner identical to that of the embodiment shown in FIGS. 11-17. Thediaphragm 84a is preferably made of a material having sufficientstrength and flexibility to perform the following functions: (1) act asa seal; (2) resist rupture under pressure during operation of thelancing assembly; (3) allow the lancing assembly to thrust a lancet intothe skin of a patient; and (3) allow the lancing assembly to retract toits initial pre-thrust position after the thrusting step.

The components of the lancing assemblies in FIGS. 11-19 must be of ashape and size to conform with the dimensional envelope available forthe lancing assembly. Proper design of the components is also animportant factor in achieving acceptable lancing results in the skin.Other important factors are the performance of the three-way valve(i.e., valve flow resistance and switching time) and the air pressureenvironment in which the lancing assembly operates, as discussed below.The components for constructing the lancing assembly are commerciallyavailable, and one of ordinary skill in the art would be expected tohave sufficient ability to select the proper components fromcommercially available sources.

Lancing results are believed to be influenced by three main parameters:(1) lancet speed during impact with the skin, (2) inertial mass of thelancet/piston combination of the lancing assembly, and (3) shape andsize of the lancet needle. The third parameter is not addressed by thelancing assembly of this invention because the assembly is expected tofunction with most commercially available lancet assemblies, such as the"BD ULTRA-FINE" (Becton-Dickinson) and the "ULTRATLC" (MediSense)brands. The first and second parameters are greatly affected by thegeometrical shapes and weights of the components in the lancingassembly, although the precise influence of lancet speed and inertialmass on lancing performance are not well understood. However, goodlancing performance has been observed with conventional devices, whichhave an inertial mass typically from 1.0 gram to 2.0 grams and deliver apeak lancet speed ranging from 3 m/sec to 5 m/sec.

A general mathematical expression that relates the lancet speed to thedesign of the lancing assembly and the pressure environment can beformulated from physical laws as follows:

    M*a(t)=A*[P.sub.c (t)-P.sub.v (t)]-K.sub.s *[x(t)+X.sub.s ]-Ff(t)

where

    ______________________________________                                        t        =         elapsed time                                               M        =         total inertial mass (piston + lancet                                          assembly)                                                  a(t)     =         translational acceleration of the                                             lancet at time = t                                         P.sub.c (t)                                                                            =         air pressure acting on the top                                                surface of the piston at time = t                          P.sub.v (t)                                                                            =         air pressure opposing the action of                                           the piston at time = t                                     A        =         projected surface area of the piston                                          acted upon by P.sub.c (t) and P.sub.v (t)                  K.sub.s  =         spring rate constant of the return                                            spring                                                     x(t)     =         translational displacement of the                                             lancet at time = t                                         X.sub.s  =         initial displacement of the return                                            spring                                                     Ff(t)    =         friction force of the piston seal at                                          time = t                                                   P.sub.c (t)-P.sub.v (t)                                                                =         differential pressure level which                                             accelerates the piston at time = t                         ______________________________________                                    

Solution of the foregoing expression for lancet displacement (x) vs.time (t), from which lancet speed as a function of time can bedetermined, requires many auxiliary equations in the field ofthermodynamics and compressible flow, which incorporate design detailsof the invention and the three-way valve. In general, the lancet speed(U_(p)) at the time of impact on the skin can be expressed in terms ofthe following variables:

    U.sub.p =F[A,M,S,X.sub.p,K.sub.s,X.sub.s,C.sub.v,Dt.sub.v,V.sub.c,V.sub.v, P.sub.a, P.sub.v,T.sub.a,Ff]

where

    ______________________________________                                        A     =         effective surface area of the piston on                                       which air pressure acts                                       M     =         total inertial mass (piston + lancet assembly)                S     =         stroke distance of the piston                                 X.sub.p                                                                             =         lancet displacement when impact with                                          skin occurs (X.sub.p < S)                                     K.sub.s                                                                             =         spring rate constant of the return                                            spring                                                        X.sub.s                                                                             =         initial displacement of the return spring                     C.sub.v                                                                             =         flow coefficient of the three-way valve                                       when activated                                                Dt.sub.v                                                                            =         switching time of the three-way valve                                         (time to fully activate)                                      V.sub.c                                                                             =         initial air volume between the piston and                                     three-way valve                                               V.sub.v                                                                             =         initial cavity volume of the apparatus                                        (i. e., measured volume of the cavity prior                                   to actuation of the lancet)                                   P.sub.a                                                                             =         pressure level of the high-pressure air                                       source                                                        P.sub.v                                                                             =         initial pressure level of the cavity of the                                   apparatus (i. e., measured pressure of low                                    pressure air source prior to actuation of                                     the lancet)                                                   T.sub.a                                                                             =         air temperature level                                         Ff    =         friction force profile of the piston seal                                     (typically varies as a function of the                                        displacement of the piston)                                   ______________________________________                                    

Maximizing the lancet speed within a specified stroke distance of thepiston (S) is accomplished by selecting a three-way valve with high flowcoefficient (C_(v)) and rapid switching time (Dt_(v)), by optimizing thesurface area of the piston (A) and initial air volume between the pistonand three-way valve (V_(c)), by minimizing the total inertial mass (M),the spring force (K_(s), X_(s)), and the friction force profile of thepiston seal (Ff), by ensuring adequate initial cavity volume (V_(v)),and by applying as much pressure differential (P_(a) -P_(v)) aspermitted by the apparatus.

The lancing assembly that utilizes differential gas pressure offersseveral advantages over conventional lancing assemblies. The advantagesare brought about by using differential gas pressure rather than acompressed spring to thrust the lancet into the skin. One advantage isthat the lancet does not need to be manually cocked by the user beforeuse. This simplifies usage and permits sequential lancing of the targetskin to provide greater access to blood. Cocking is not required becausethe gas providing differential gas pressure is vented from the lancingassembly after use, thereby allowing the piston biasing means to forcethe lancet back to its original position. Another advantage is that thelancing assembly does not need to be mechanically triggered. Thissimplifies the design of the device and protects against accidentaltriggering by the user if the device is mishandled. A separatetriggering mechanism is not required because the differential gaspressure functions to both initiate and execute the lancing process.Still another advantage is that the lancing assembly fully retracts thelancet when lancing is not in progress. This minimizes exposure of theuser to the sharp lancet when handling the device in preparation for useor after use. Full retraction of the lancet is accomplished by thepiston biasing means after the gas that provided the differential gaspressure has been vented from the lancing assembly.

The vacuum pump 14 is connected to the lancing assembly 16 by anevacuation tube 24. The air that is evacuated from the lancing assembly16 by the vacuum pump 14 is removed via the evacuation tube 24. Theevacuation tube 24 is typically made from a polymeric material. A checkvalve 26 is placed between the vacuum pump 14 and the lancing assembly16 at a point in the evacuation tube 24 to prevent air removed from thelancing assembly 16 by the vacuum pump 14 from flowing back to thelancing assembly 16 and adversely affecting the vacuum.

A source of power for the vacuum pump 14 can be disposed within thehousing 12. A source of power suitable for the device of this inventionis a battery 18. Alternatively, an external source of power can be usedto operate the vacuum pump 14. The power source is actuated by theelectronics 20, which, in turn, is actuated by the switch 22.

The electronics 20 may incorporate a microprocessor or microcontroller.The function of the electronics 20 is to switch power on and off tooperate the various components in the apparatus. These componentsinclude, but are not limited to, the vacuum pump 14. The electronics 20can also be use to switch power on and off to operate components inalternative embodiments, e.g., heating elements, lancets, indicatingdevices, and valves. Electronics suitable for this invention is the"TATTLETALE MODEL 5 F" controller/data logger, commercially availablefrom Onset Computer Corporation, 536 MacArthur Blvd. P.O. Box 3450,Pocasset, Mass. 02559-3450. Auxiliary electronic devices, such as powertransistors, pressure monitors, and OP-Amps (operational amplifiers),may also be required in order to provide an interface between thecontroller and the operational components. All electronics required forthis invention are well-known to one of ordinary skill in the art andare commercially available. Auxiliary electronic devices suitable foruse in this invention include the following components:

    ______________________________________                                        Component   Source          Catalog Number                                    ______________________________________                                        Mosfet Drivers                                                                            International Rectifier                                                                       IRLD024                                                       El Segundo, CA                                                    Op-Amp      National Semiconductor                                                                        LM358                                                         Santa Clara, CA                                                   Status LED  Hewlett-Packard HLMPD150                                                      Newark Electronics                                                            Schaumburg, IL                                                    Pressure Sensor                                                                           Sensym, Inc.    SDX15D4                                                       Milpitas, CA                                                      ______________________________________                                    

FIG. 3 illustrates by way of a block diagram how the foregoingelectronic components can be arranged to carry out the method of thepresent invention.

Operation of the blood extraction device 10 will now be described.Referring now to FIGS. 1, 2 and 3, the nosepiece 30 of the lancingassembly 16 is applied to the surface of the skin, designated herein bythe letter "S". The end of the nosepiece 30 that contacts the skin isequipped with a seal 32. The purpose of the seal 32 is to prevent airfrom leaking into blood extraction chamber 34, so that the vacuum pump14 can provide sufficient suction action for increasing the availabilityof blood to the area of the skin from which the sample is to beextracted, stretching the skin, and extracting the sample of blood fromthe unobstructed opening in the skin. The seal 32 surrounds an opening33 in the nosepiece 30. The opening 33 in the nosepiece allowscommunication between the surface of the skin and a blood extractionchamber 34 in the nosepiece 30. The seal 32 is preferably made of arubber or an elastomeric material. FIG. 4 illustrates an alternativeposition for the seal 32. In FIG. 4, the seal is designated by thereference numeral 32'. The remaining parts of FIG. 4 are the same asthose of FIG. 2, and, accordingly, retain the same reference numerals aswere used in FIG. 2.

The switch 22 is actuated, typically by being pressed, therebyactivating the electronics 20, which starts the vacuum pump 14. Thevacuum pump 14 then provides a suction action. The suction action of thevacuum pump 14 causes the skin circumscribed by the seal 32 to becomeengorged with blood. Engorgement of the skin with blood is accompaniedby a stretching of and rising up of the skin up to opening 33.

After an appropriate period of time, which is typically pre-set by theprogrammer of the electronics, the lancing assembly 16 is triggered,thereby causing the lancet 36 to penetrate the skin that has risen up tothe opening 33 and that is engorged with blood. The lancet 36 ispreferably triggered automatically, by a solenoid valve 38 that causes avacuum-actuated piston (not shown) to trigger the lancet 36. The lancet36 is then retracted, preferably automatically. Thereupon, the bloodflows out of the unobstructed opening resulting from the lancet 36, and,aided by the vacuum generated by the vacuum pump 14, is collected. Whensufficient blood has been collected or a pre-set time interval haspassed, the electronics 20 causes the vacuum pump 14 to stop. The device10 can then be removed from the surface of the skin after anothersolenoid valve (not shown because it is hidden under solenoid valve 38)is opened to vent the vacuum to allow ease of removal of the device fromthe surface of the skin. Solenoid valves suitable for use with theapparatus described herein are commercially available from The LeeCompany, Essex, CT and have the part number LHDA0511111H.

FIGS. 15A, 15B, and 15C illustrate an installation of the lancingassembly of FIGS. 11 and 12 inside a hypothetical apparatus 91. Thelancing assembly 60 is fixed inside a cavity 92 of the apparatus 91 andfitted with a three-way solenoid valve 74 and a standard disposablelancet assembly 93 as shown. The lancet assembly 93 comprises a lancet93a, which is inserted into a molded plastic body 93b. The apparatus 91has a lower passage 94 through which the lancet assembly 93 can move toform an unobstructed opening in the area of the skin "S" that iscircumscribed by a circular opening 94a (shown by dashed line) in thelower passage. A side port 95 on a wall 96 of the apparatus 91 connectsinlet port 76 on the lancing assembly 60 to ambient air surrounding theapparatus 91. The apparatus 91 also has a vacuum source 97 to maintainthe air pressure in the cavity 92 at the level at which the apparatusoperates, and a voltage source 98 to selectively activate the three-waysolenoid valve 74. With voltage off, the three-way solenoid valve 74connects the bore 80 of the lancing assembly 60 with the cavity 92 viaexit port 82, causing the piston 64 to experience no differential airpressure.

In the "Ready" mode (FIG. 15A), the lower passage 94 of the apparatus 91is placed across the target skin. The vacuum pressure of the apparatusreaches operational level P_(v), which is substantially less thanambient pressure P_(a) (e.g., P_(v) =-7.5 psig, P_(a) =0 psig). Thetarget skin is partially drawn into the lower passage 94 by vacuumpressure P_(v). The voltage of the three-way solenoid valve 74 isinitially off, thereby preventing ambient air from entering the lancingassembly 60, allowing the return spring 68 to maintain the lancet 93a atits maximum distance (e.g., 10 mm) from the skin.

In the "Lance" mode (FIG. 15B), the three-way solenoid valve 74 isactivated by the voltage source 98, which allows ambient air to flowcontinuously through the side port 95 of the apparatus 91 through theinlet port 76 and then through the bore port 78 into the bore 80 of thelancing assembly 60. The flow of ambient air increases the air pressurein the bore 80, causing a differential air pressure to act on the piston64. The differential air pressure acting on the piston 64 rapidlyincreases and overcomes the opposing force of the return spring 68 andthe friction of the o-ring 84, causing the combined mass of the piston64 and lancet assembly 93 (e.g., 1.5 grams) to thrust toward the targetskin. The lancet 93a contacts the skin in a short period of time (e.g.,6 msec) and reaches sufficient speed (e.g., 3.5 m/sec) to form anopening in the skin and to penetrate to a specified depth (e.g., 1.5mm). The opening in the skin is complete when the thrusting motion ofthe lancet assembly 93 is halted by some halting means. Suitable meansfor halting the lancet assembly 93 include, but are not limited to, thecap 70 within the lancing assembly 60, which, in effect, limits thestroke distance of the piston 64, and a lancet stop, as will bedescribed in FIG. 20.

In the "Return" mode (FIG. 15C), the lancet 93a begins retracting fromthe skin when the voltage of the solenoid is shut off, which occursafter a predefined dwell time (e.g., 10 msec). With voltage off, thethree-way solenoid valve 74 reconnects the bore 80 to exit port 82 inthe lancing assembly 60 via the bore port 78, causing air from the bore80 to vent quickly (e.g., 15 msec) through the three-way solenoid valve74 and out through exit port 82 into the cavity 92, which containslow-pressure air, provided in the apparatus by the vacuum source 97.During venting, the compressed return spring 68 overcomes the combinedforce of the differential air pressure and the friction of the o-ring 84to move the piston 64 and the lancet assembly 93 back to the startingposition. The lancing cycle, which requires a total of 25 msec in thishypothetical apparatus, is then complete.

The solenoid is driven by the voltage system of the apparatus. Each timethe voltage is turned on and then turned off (i.e., one pulse), thethree-way solenoid valve 74 switches internally, first directing flow ofair into the lancing assembly 60 and then away from the lancing assembly60. This switching causes the lancet to be thrust into the target skintissue, then to be retracted away from the target skin tissue. Bypulsing the solenoid repeatedly with voltage, the lancing process isrepeated. This feature has been termed "repetitive lancing."

The resulting opening formed in the skin is similar to that achievedwith conventional lancing devices; such an opening is capable ofallowing a volume of biological fluid (e.g., 3 μL capillary blood) to besampled for analysis.

The lancing process illustrated in FIGS. 15A, 15B, 15C can be repeatedas many times as desired using the same lancet and without disturbingthe device or target skin. With the skin still held in place by vacuumsuction, the solenoid voltage can be pulsed as needed to lance thetarget area more than one time. Repetitive lancing has two potentialbenefits. First, it can be coordinated with an indexing system in theapparatus to lance a matrix of sites on the target skin for additionalaccess to biological fluid. Second, it can increase the lancing successrate at or near a single site, by sequentially lancing into the skinuntil the desired amount of blood is obtained.

The blood is preferably directly collected on the application zone of aglucose detector, e.g., a reflectance strip or biosensor. The blood canthen be used as the sample for a determination of glucose concentrationin blood. Alternatively, the blood can be collected by other collectiondevices, such as, for example, a capillary tube or absorbent paper.

The apparatus of the present invention can include a glucose detectorfor analyzing the blood sample extracted by the apparatus. Glucosedetectors are well-known in the art. With respect to glucose monitoring,there are two major categories of glucose detectors--reflectometers andbiosensors. Representative examples of reflectometers suitable for thisinvention are described in U.S. Pat. No. 4,627,445, incorporated hereinby reference. Representative examples of biosensors suitable for thisinvention are described in U.S. Pat. No. 5,509,410, incorporated hereinby reference.

The glucose detector is preferably disposed in the nosepiece 30 of thelancing assembly 16. The glucose detector must be located at a positionsufficiently close to the site of blood extraction so that the quantityof extracted blood collected will be sufficient to carry out a standardglucose monitoring test. Typically, this distance will preferably be nomore than 5 mm from the site of blood extraction, more preferably nomore than 3 mm from the site of blood extraction, most preferably nomore than 1 mm from the site of blood extraction. Care must be taken inthe placement of the glucose detector so that the detector does notadversely affect the vacuum, when a vacuum is employed to aid in theextraction of blood. In addition, the glucose detector 40 should bemodified, if necessary, so that the blood collected in the collectionzone of the glucose detector is capable of being used to activate theglucose detector.

FIG. 2 also illustrates a manner for disposing a glucose detector 40 inthe nosepiece 30 of the lancing assembly 16.

FIGS. 5, 6, 7, 8, 9, and 10 illustrate various alternative embodimentsof the apparatus of this invention. In FIG. 5, blood extraction device100 comprises a housing 102. The housing 102 is separable into twoportions, a receiving portion 102a and a projecting portion 102b. Agasket 104 is provided to seal the portions 102a and 102b of the housing102 and to aid in separation of the receiving portion 102a from theprojecting portion 102b. The receiving portion 102a forms a tight fitwith the projecting portion 102b by means of friction. Projectingelements 102c and 102d are used to guide the projecting portion 102binto the receiving portion 102a. Disposed within the housing 102 are avacuum pump (not shown), a lancing assembly 108, a battery (not shown),and electronics (not shown). A switch 109 is provided to activate theelectronics. The vacuum pump is connected to the lancing assembly 108 byan evacuation tube (not shown). A check valve (not shown) is placedbetween the vacuum pump and the lancing assembly 108.

During the process of obtaining the sample, the receiving portion 102aand the projecting portion 102b are fitted tightly together. The area ofthe receiving portion 102a of the housing 102 of the device 100 that isto contact the skin is equipped with a seal 110. The seal 110 surroundsan opening 112 in the receiving portion 102a. The opening 112 in thereceiving portion 102a allows communication between the surface of theskin and a blood extraction chamber adjacent to a glucose detector 114,shown here in the shape of a strip. When in use, the device 100 ispositioned so that the lancing assembly 108 is placed over the region onthe surface of the skin from which the sample is to be obtained. Inorder to obtain the sample of blood, the receiving portion 102a of thehousing 102 of the device 100 is placed against the skin, whereby theseal 110 allows a satisfactory vacuum to be effected. The switch 109 isactuated, typically by being pressed, thereby activating theelectronics, which starts the vacuum pump. The vacuum pump then providesa suction action. The suction action of the vacuum pump causes the skincircumscribed by the seal 110 to become engorged with blood. Engorgementof the skin with blood is accompanied by a stretching of and rising upof the skin up to the opening 112. After an appropriate period of time,which is typically pre-set by the programmer of the electronics, thelancing assembly 108 is triggered, thereby causing the lancet 116 topenetrate the skin that has risen up to the opening 112 and that isengorged with blood. The lancet 116 is preferably triggeredautomatically, by a solenoid valve (not shown) that causes avacuum-actuated piston (not shown) to trigger the lancet 116. Theremaining steps of the process relating to collection of a sample ofblood are substantially similar to the steps described in the embodimentshown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 5, the glucose detector 114 is insertedinto a slot 118 in the projecting portion 102b of the housing 102. Thereceiving portion 102a of the housing 102 causes the glucose detector114 to be moved into its proper position for testing. The resultsobtained from the glucose detector 114 can be displayed on a screen 120,typically a conventional liquid crystal digital display. The receivingportion 102a is separated from the projecting portion 102b when thelancet 116 or glucose detector 114 is being replaced. The receivingportion 102a is fitted tightly to the projecting portion 102b during theprocess of obtaining a sample of blood.

The relative positions of the vacuum pump, the battery, the electronics,the evacuation tube, the check valve, the solenoid valves, and thevacuum-actuated piston are substantially similar to the relativepositions of these components as described in the embodiments shown inFIGS. 1 and 2. In FIG. 6, blood extraction device 200 comprises ahousing 202. The housing 202 comprises a door portion 202a that isattached to the remaining portion 202b of the housing 202 by a hinge206. A gasket 207 is provided to seal the housing 202 when the doorportion 202a is closed. The door portion 202a can be closed by pivotingit around the hinge 206. When the door portion 202a is closed, theconvex portion 202c of the door portion 202a fits precisely into theconcave portion 202d of the remaining portion 202b of the housing 202.The remaining edges of the door portion 202a fit tightly against theremaining edges of the remaining portion 202b of the housing 202.Disposed within the housing 202 are a vacuum pump (not shown), a lancingassembly 208, a battery (not shown), and electronics (not shown). Aswitch (not shown) is provided to activate the electronics. The vacuumpump is connected to the lancing assembly 208 by an evacuation tube (notshown). A check valve (not shown) is placed between the vacuum pump andthe lancing assembly 208.

During the process of obtaining the sample, the door portion 202a isclosed. The area of the door portion 202a of the housing 202 of thedevice 200 that is to contact the skin is equipped with a seal (notshown). The seal surrounds an opening 212 in the door portion 202a. Theopening 212 in the door portion 202a allows communication between thesurface of the skin and a blood extraction chamber adjacent to a glucosedetector 214, shown here in the shape of a strip. When in use, thedevice 200 is positioned so that the lancing assembly 208 is placed overthe region on the surface of the skin from which the sample is to beobtained. In order to obtain the sample of blood, the door portion 202aof the housing 202 of the device 200 is placed against the skin, wherebythe seal allows a satisfactory vacuum to be effected. The switch isactuated, typically by being pressed, thereby activating theelectronics, which starts the vacuum pump. The vacuum pump then providesa suction action. The suction action of the vacuum pump causes the skincircumscribed by the seal to become engorged with blood. Engorgement ofthe skin with blood is accompanied by a stretching of and rising up ofthe skin up to the opening 212. After an appropriate period of time,which is typically pre-set by the programmer of the electronics, thelancing assembly 208 is triggered, thereby causing the lancet 216 topenetrate the skin that has risen up to the opening 212 and that isengorged with blood. The lancet 216 is preferably triggeredautomatically, by a solenoid valve (not shown) that causes avacuum-actuated piston (not shown) to trigger the lancet 216. Theremaining steps of the process relating to collection of a sample ofblood are substantially similar to the steps described in the embodimentshown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 6, the glucose detector 214 is insertedinto slots 218a and 218b of the housing 202. The results obtained fromthe glucose detector 214 can be displayed on screen 220, typically aconventional liquid crystal digital display. The door portion 202a isopened when the lancet 216 or glucose detector 214 is being replaced.The door portion 202a is closed during the process of obtaining a sampleof blood.

The relative positions of the vacuum pump, the battery, the electronics,the switch, the evacuation tube, the check valve, the seal, the solenoidvalves, and the vacuum-actuated piston are substantially similar to therelative positions of these components as described in the embodimentsshown in FIGS. 1 and 2.

In FIG. 7, blood extraction device 300 comprises a housing 302. Thehousing 302 comprises a door portion 302a that is attached to theremaining portion 302b of the housing 302 by a hinge 306. A gasket 307is provided to seal the housing 302 when the door portion 302a isclosed. The door portion 302a can be closed by pivoting it around thehinge 306. When the door portion 302a is closed, the convex portion 302cof the door portion 302a fits precisely into the concave portion 302d ofthe remaining portion 302b of the housing 302. The remaining edges ofthe door portion 302a fit tightly against the remaining edges of theremaining portion 302b of the housing 302. Disposed within the housing302 are a vacuum pump (not shown), a lancing assembly 308, a battery(not shown), and electronics (not shown). A switch (not shown) isprovided to activate the electronics. The vacuum pump is connected tothe lancing assembly 308 by an evacuation tube (not shown). A checkvalve (not shown) is placed between the vacuum pump and the lancingassembly 308.

During the process of obtaining the sample, the door portion 302a isclosed. The area of the door portion 302a of the housing 302 of thedevice 300 that is to contact the skin is equipped with a seal (notshown). The seal surrounds an opening 312 in the door portion 302a. Theopening 312 in the door portion 302a allows communication between thesurface of the skin and a blood extraction chamber adjacent to a glucosedetector 314, shown here in the shape of a strip. When in use, thedevice 300 is positioned so that the lancing assembly 308 is placed overthe region on the surface of the skin from which the sample is to beobtained. In order to obtain the sample of blood, the door portion 302aof the housing 302 of the device 300 is placed against the skin, wherebythe seal allows a satisfactory vacuum to be effected. The switch isactuated, typically by being pressed, thereby activating theelectronics, which starts the vacuum pump. The vacuum pump then providesa suction action. The suction action of the vacuum pump causes the skincircumscribed by the seal to become engorged with blood. Engorgement ofthe skin with blood is accompanied by a stretching of and rising up ofthe skin up to the opening 312. After an appropriate period of time,which is typically pre-set by the programmer of the electronics, thelancing assembly 308 is triggered, thereby causing the lancet 316 topenetrate the skin that has risen up to the opening 312 and that isengorged with blood. The lancet 316 is preferably triggeredautomatically, by a solenoid valve (not shown) that causes avacuum-actuated piston (not shown) to trigger the lancet 316. Theremaining steps of the process relating to collection of a sample ofblood are substantially similar to the steps described in the embodimentshown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 7, the glucose detector 314 is insertedinto a slot 318 of the housing 302. The results obtained from theglucose detector 314 can be displayed on screen 320, typically aconventional liquid crystal digital display. In FIG. 7, connections 322for the electronics are shown. The door portion 302a is opened when thelancet 316 or glucose detector 314 is being replaced. The door portion302a is closed during the process of obtaining a sample of blood.

The relative positions of the vacuum pump, the battery, the electronics,the switch, the evacuation tube, the check valve, the seal, the solenoidvalves, and the vacuum-actuated piston are substantially similar to therelative positions of these components as described in the embodimentsshown in FIGS. 1 and 2.

In FIG. 8, blood extraction device 400 comprises a housing 402. Thehousing 402 comprises a door portion 402a that is attached to theremaining portion 402b of the housing 402 by a hinge 406. A gasket 407is provided to seal the housing 402 when the door portion 402a isclosed. The door portion 402a can be closed by pivoting it around thehinge 406. When the door portion 402a is closed, the convex portions402c and 402d of the door portion 402a fit precisely into the concaveportions 402e and 402f, respectively, of the remaining portion 402b ofthe housing 402. The remaining edges of the door portion 402a fittightly against the remaining edges of the remaining portion 402b of thehousing 402. Disposed within the housing 402 are a vacuum pump (notshown), a lancing assembly 408, a battery (not shown), and electronics(not shown). A switch 409 is provided to activate the electronics. Thevacuum pump is connected to the lancing assembly 408 by an evacuationtube (not shown). A check valve (not shown) is placed between the vacuumpump and the lancing assembly 408.

During the process of obtaining the sample, the door portion 402a isclosed. The area of the door portion 402a of the housing 402 of thedevice 400 that is to contact the skin is equipped with a seal (notshown). The seal surrounds an opening 412 in the door portion 402a. Theopening 412 in the door portion 402a allows communication between thesurface of the skin and a blood extraction chamber adjacent to a glucosedetector 414, shown here in the shape of a strip. When in use, thedevice 400 is positioned so that the lancing assembly 408 is placed overthe region on the surface of the skin from which the sample is to beobtained. In order to obtain the sample of blood, the door portion 402aof the housing 402 of the device 400 is placed against the skin, wherebythe seal allows a satisfactory vacuum to be effected. The switch 409 isactuated, typically by being pressed, thereby activating theelectronics, which starts the vacuum pump. The vacuum pump then providesa suction action. The suction action of the vacuum pump causes the skincircumscribed by the seal to become engorged with blood. Engorgement ofthe skin with blood is accompanied by a stretching of and rising up ofthe skin up to the opening 412. After an appropriate period of time,which is typically pre-set by the programmer of the electronics, thelancing assembly 408 is triggered, thereby causing the lancet 416 topenetrate the skin that has risen up to the opening 412 and that isengorged with blood. The lancet 416 is preferably triggeredautomatically, by a solenoid valve (not shown) that causes avacuum-actuated piston (not shown) to trigger the lancet 416. Theremaining steps of the process relating to collection of a sample ofblood are substantially similar to the steps described in the embodimentshown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 8, the glucose detector 414 is insertedinto a slot 418 of the housing 402. In this embodiment, it is shown thatglucose detector 14 can be rotated 90° between two positions to simplifyinsertion and replacement thereof. The results obtained from the glucosedetector 414 can be displayed on screen 420, typically a conventionalliquid crystal digital display. The door portion 402a is opened when thelancet 416 or glucose detector 414 is being replaced. The door portion402a is closed during the process of obtaining a sample of blood.

The relative positions of the vacuum pump, the battery, the electronics,the evacuation tube, the check valve, the seal, the solenoid valves, andthe vacuum-actuated piston are substantially similar to the relativepositions of these components as described in the embodiments shown inFIGS. 1 and 2.

In FIG. 9, blood extraction device 500 comprises a housing 502. Thehousing 502 comprises a cover portion 502a that is attached to theremaining portion 502b of the housing 502 by a hinge 506. A gasket 507is provided to seal the housing 502 when the cover portion 502a isclosed. The cover portion 502a can be closed by pivoting it around thehinge 506. When the cover portion 502a is closed, edges 502c of thecover portion 502a tightly fit against edges 502d of the remainingportion 502b of the housing 502. Disposed within the housing 502 are avacuum pump (not shown), a lancing assembly 508, a battery (not shown),and electronics (not shown). A switch (not shown) is provided toactivate the electronics. The vacuum pump is connected to the lancingassembly 508 by an evacuation tube (not shown). A check valve (notshown) is placed between the vacuum pump and the lancing assembly 508.

During the process of obtaining the sample, the cover portion 502a isclosed. The cover portion 502a of the housing 502 of the device 500 thatis to contact the skin is equipped with a seal 511. The seal 511surrounds an opening 512 in the cover portion 502a. The opening 512 inthe cover portion 502a allows communication between the surface of theskin and a blood extraction chamber adjacent to a glucose detector 514,shown here in the shape of a strip. When in use, the device 500 ispositioned so that the lancing assembly 508 is placed over the region onthe surface of the skin from which the sample is to be obtained. Inorder to obtain the sample of blood, the cover portion 502a of thehousing 502 of the device 500 is placed against the skin, whereby theseal allows a satisfactory vacuum to be effected. The switch isactuated, typically by being pressed, thereby activating theelectronics, which starts the vacuum pump. The vacuum pump then providesa suction action. The suction action of the vacuum pump causes the skincircumscribed by the seal to become engorged with blood. Engorgement ofthe skin with blood is accompanied by a stretching of and rising up ofthe skin up to the opening 512. After an appropriate period of time,which is typically pre-set by the programmer of the electronics, thelancing assembly 508 is triggered, thereby causing the lancet 516 topenetrate the skin that has risen up to the opening 512 and that isengorged with blood. The lancet 516 is preferably triggeredautomatically, by a solenoid valve (not shown) that causes avacuum-actuated piston (not shown) to trigger the lancet 516. Theremaining steps of the process relating to collection of a sample ofblood are substantially similar to the steps described in the embodimentshown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 9, the glucose detector 514 is insertedinto a slot 518 of the housing 502. The results obtained from theglucose detector 514 can be displayed on screen 520, typically aconventional liquid crystal digital display. The cover portion 502a isopened when the lancet 516 or glucose detector 514 is being replaced.The cover portion 502a is closed during the process of obtaining asample of blood.

The relative positions of the vacuum pump, the battery, the electronics,the switch, the evacuation tube, the check valve, the solenoid valves,and the vacuum-actuated piston are substantially similar to the relativepositions of these components as described in the embodiments shown inFIGS. 1 and 2.

In FIG. 10, blood extraction device 600 comprises a housing 602. Thehousing 602 comprises a cover portion 602a that is attached to theremaining portion 602b of the housing 602 by a hinge 606. A gasket 607is provided to seal the housing 602 when the cover portion 602a isclosed. The cover portion 602a can be closed by pivoting it around thehinge 606. When the cover portion 602a is closed, edges 602c of thecover portion 602a tightly fit against edges 602d of the remainingportion 602b of the housing 602. Disposed within the housing 602 are avacuum pump (not shown), a lancing assembly 608, a battery (not shown),and electronics (not shown). A switch 609 is provided to activate theelectronics. The vacuum pump is connected to the lancing assembly 608 byan evacuation tube (not shown). A check valve (not shown) is placedbetween the vacuum pump and the lancing assembly 608.

During the process of obtaining the sample, the cover portion 602a isclosed. The cover portion 602a of the housing 602 of the device 600 thatcontacts the skin is equipped with a seal 611. The seal 611 surrounds anopening 612 in the cover portion 602a. The opening 612 in the coverportion 602a allows communication between the surface of the skin and ablood extraction chamber adjacent to a glucose detector 614, shown herein the shape of a strip. When in use, the device 600 is positioned sothat the lancing assembly 608 is placed over the region on the surfaceof the skin from which the sample is to be obtained. In order to obtainthe sample of blood, the cover portion 602a of the housing 602 of thedevice 600 is placed against the skin, whereby the seal allows asatisfactory vacuum to be effected. The switch is actuated, typically bybeing pressed, thereby activating the electronics, which starts thevacuum pump. The vacuum pump then provides a suction action. The suctionaction of the vacuum pump causes the skin circumscribed by the seal tobecome engorged with blood. Engorgement of the skin with blood isaccompanied by a stretching of and rising up of the skin up to theopening 612. After an appropriate period of time, which is typicallypre-set by the programmer of the electronics, the lancing assembly 608is triggered, thereby causing the lancet 616 to penetrate the skin thathas risen up to the opening 612 and that is engorged with blood. Thelancet 616 is preferably triggered automatically, by a solenoid valve(not shown) that causes a vacuum-actuated piston (not shown) to triggerthe lancet 616. The remaining steps of the process relating tocollection of a sample of blood are substantially similar to the stepsdescribed in the embodiment shown in FIGS. 1, 2, 3, and 4.

In the embodiment shown in FIG. 10, the glucose detector 614 is insertedinto a slot 618 of the housing 602. The results obtained from theglucose detector 614 can be displayed on screen 620, typically aconventional liquid crystal digital display. The cover portion 602a isopened when the lancet 616 or glucose detector 614 is being replaced.The cover portion 602a is closed during the process of obtaining asample of blood.

The relative positions of the vacuum pump, the battery, the electronics,the switch, the evacuation tube, the check valve, the solenoid valves,and the vacuum-actuated piston are substantially similar to the relativepositions of these components as described in the embodiments shown inFIGS. 1 and 2.

In each of the embodiments shown in the foregoing FIGS. 5, 6, 7, 8, 9,and 10, the housing, vacuum pump, lancing assembly, battery,electronics, evacuation tube, check valve, nosepiece, seal, opening,blood extraction chamber, lancet, and solenoid valve can be made of thesame materials as the corresponding components of the apparatus shown inFIGS. 1, 2, and 3. The gaskets 104, 207, 307, 407, 507, and 607 can bemade of the same material as the seal. The components shown in theforegoing FIGS. 5, 6, 7, 8, 9, and 10 function in the same manner as dothe corresponding components of the apparatus shown in FIGS. 1, 2, and3.

It should be noted that the designs of the various housings shown inFIGS. 5, 6, 7, 8, 9, and 10 can be modified without substantiallyaffecting the functioning of the components disposed within the housingor on the surface of the housing. For example, the shapes of thehousings, the shapes of the door portions of the housings, the shapes ofthe cover portions of the housings, and the shapes of the remainingportions of the housings can be modified without departing from thescope and spirit of this invention.

This invention provides numerous advantages over blood extractiondevices of the prior art. Among these advantages are the following:

1. Ability to use parts of the body, other than the finger, as a sitefor the extraction of blood;

2. Reduction of pain by eliminating the need to lance the finger;

3. Increase in speed of collection of blood samples by means ofpre-treatment comprising a combination of stretching of the skin inconjunction with heat or vacuum or both heat and vacuum;

4. Incorporation of glucose detector in apparatus for extracting theblood sample.

The following examples illustrate various features of the presentinvention but is not intended to in any way limit the scope of theinvention as set forth in the claims. In the following examples, theterm "pierce" and forms thereof and the term "puncture" and formsthereof are used interchangeably. Although the expression "glucosedetector" is used herein, one of ordinary skill in the art willrecognize that the apparatus and methods of the present invention canalso be used to perform other diagnostic tests.

EXAMPLES Example 1

This example illustrates that greater volumes of blood can be extractedand collected by applying a vacuum, pulsed or continuous, after piercingthan can be extracted and collected when no vacuum is applied. No vacuumwas applied prior to piercing.

Each of four people had his forearm (dorsal forearm) punctured fourtimes (at four different positions on the forearm) with a "BDULTRA-FINE" lancet in a "MEDISENSE" lancet assembly (Model no. 97101) attwo different levels of vacuum (-2.5 psig and -5.0 psig) and for eachdifferent vacuum pulsing frequencies (0, 0.2, 0.8, 3.2, 12.8, 25, 100hertz). The vacuum was applied with a pipette tip having a diameter of 8mm ("RAININ RT-200"). Four control runs without a vacuum were alsocarried out (one puncture per person). A total of 60 punctures perperson were carried out. Accordingly, it can be seen that a total of 240runs were carried out.

The vacuum was applied for a duration of 30 seconds after puncturing.Blood was collected into capillary tubes. In the control runs, thesamples were extracted and collected 30 seconds after puncturing. Theamount of blood collected was determined by measuring the length ofblood in the tubes. The percentage of collections in which the volume ofblood collected exceeded 1.0 μL was calculated. Sensation of pain wasalso recorded. The following pain scores were used:

Pain of 1=person did not feel anything or not sure if anything was felt

Pain of 2=person felt definite prick, not as painful as piercing offinger by standard finger lancet

Pain of 3=person felt definite pain, approximately equal to a piercingof finger by standard finger lancet

Blood collection results are set forth in TABLE I.

                                      TABLE I                                     __________________________________________________________________________                   Percent of      Percent of                                            Average samples Average samples                                               volume of                                                                             having >1 μL                                                                       volume of                                                                             having >1 μL                                       blood sample                                                                          of blood                                                                              blood sample                                                                          of blood                                       Frequency                                                                            collected at                                                                          collected at                                                                          collected at                                                                          collected at                                   (hertz)                                                                              -2.5 psig (μL)                                                                     -2.5 psig                                                                             -5.0 psig (μL)                                                                     -5.0 psig                                      __________________________________________________________________________    0      1.6     69      3.1     94                                             (Continuous)                                                                  0.2    1.1     44      3.0     94                                             0.8    1.1     63              75                                             3.2    1.5     56      3.8     75                                             12.5   1.8     75      3.1     100                                            25     2.3     75      3.2     94                                             100    2.4     81      2.7     88                                             __________________________________________________________________________

With no vacuum, average volume of blood collected was 0.8 μL and 31% ofthe samples collected contained more than 1 μL. The pain results were asfollows:

pain of 1=81%

pain of 2=17%

pain of 3=2%

The control runs (no vacuum) provided much lower volumes of bloodcollected than did the runs where vacuum was applied. Increased vacuumresulted in higher volumes of blood extracted. The pain was minimal,with only 2% of the punctures resulting in pain comparable to thatresulting from a piercing of the finger.

Example 2

This example illustrates that application of vacuum prior to piercing aswell as after piercing results in a greater volume of blood extractedthan does the application of vacuum only after piercing.

Each of four people had his forearm (dorsal forearm, middle of forearm)punctured sixteen times (at sixteen different positions on the forearm)with a "BD ULTRA-FINE" lancet in a modified "MEDISENSE" lancet assemblyat four different levels of vacuum. The four levels of vacuum used were-2.5, -5.0, -7.5, and -10.0 psig. The "MEDISENSE" lancet device wasmodified to allow vacuum to be pulled through the lancet assembly. Fourpunctures per person were carried out at each of the four levels ofcontinuous vacuum. Accordingly, it can be seen that a total of 64 runswere carried out.

Prior to puncturing, the vacuum was applied for a period of 30 seconds;subsequent to puncturing, the vacuum was applied for a period of 30seconds. The skin was under vacuum at the time the lancet was triggered.After the lancet was triggered, the lancet assembly was removed, and thevacuum was used to apply the same level of vacuum that had been used forthe vacuum prior to puncturing. The vacuum, both prior to puncturing andsubsequent to puncturing, was applied with a pipette tip having adiameter of 8 mm ("RAININ RT-200"). The pipette tip of the vacuum devicewas held level to the plane of the skin. Blood was then collected intocapillary tubes. The amount of blood collected was determined bymeasuring the length of blood in the tubes. The percentage ofcollections in which the volume of blood collected exceeded 1.0 μL wascalculated. Sensation of pain was also recorded. Blood collectionresults are set forth in TABLE II.

                  TABLE II                                                        ______________________________________                                                                  Percent of samples                                             Average volume of blood                                                                      having >1 μL of blood                            Vacuum level (psig)                                                                      sample collected (μL)                                                                     collected                                           ______________________________________                                        -2.5       4.6            94                                                  -5.0       7.8            100                                                 -7.5       9.2            100                                                 -10.0      14.0           100                                                 ______________________________________                                    

The pain results were as follows:

pain of 1=58%

pain of 2=31%

pain of 3=11%

A nearly linear relationship between level of vacuum and volume of bloodcollected was observed. The average volume of blood collected withvacuum applied prior and after piercing was approximately twice thatcollected with vacuum applied only after piercing without vacuum appliedprior to piercing. See the results of Example 1 for this comparison (7.8μL vs. 3.1 μL). The volume of blood collected was always above 1 μL forall levels of vacuum, except -2.5 psig.

Example 3

This example illustrates that localized heating of the area to bepierced followed by vacuum after piercing results in a greater volume ofblood being extracted than does extraction with only vacuum afterpiercing.

Each of four people had his forearm (dorsal forearm, middle of forearm)punctured eight times (at eight different positions on the forearm) witha "BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly with heatapplied (45° C.) prior to piercing for two different time periods, 15seconds and 60 seconds. A total of 32 runs were carried out, 16 runswhere the pre-heating duration was 15 seconds and 16 runs where thepre-heating duration was 60 seconds.

Heat was applied with a heating block, which was an aluminum blockhaving a square face covered with a "KAPTON" film heater elementcontrolled by an "OMEGA" DP 41 temperature controller using a T-typethermocouple. Vacuum was applied after each puncturing for 30 seconds at-5.0 psig. Blood was collected into capillary tubes. The amount of bloodcollected was determined by measuring the length of blood in the tubes.The percentage of collections in which the volume of blood collectedexceeded 1.0 μL was calculated. Pain was also tracked. Blood collectionresults are set forth in TABLE III.

                  TABLE III                                                       ______________________________________                                                                  Percent of samples                                  Pre-piercing heating                                                                     Average volume of blood                                                                      having >1 μL of blood                            duration (seconds)                                                                       samples collected (μL)                                                                    collected                                           ______________________________________                                        15         6.91           94                                                  60         11.6           100                                                 ______________________________________                                    

The pain results were as follows:

pain of 1=91%

pain of 2=9%

pain of 3=0%

The average volume of blood collected using a pre-heating duration of 15seconds was more than twice the average volume of blood collected at apost-puncturing vacuum level of -5.0 psig., with no pre-heating. See theresults of Example 1 for this comparison (6.91 μL vs. 3.1 μL). Theaverage volume of blood collected using a pre-heating duration of 60seconds was approximately four times the average volume of bloodcollected at a post-puncturing vacuum level of -5.0 psig, with nopre-heating. See the results of Example 1 for this comparison (11.6 μLvs. 3.1 μL).

Example 4

This example illustrates the effect that stretching the skin upwardlywith a vacuum has on the extraction of blood.

Each of four people had his forearm (dorsal forearm, middle of forearm)punctured eight times (at eight different positions on the forearm) witha "BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly. Vacuum wasapplied for a period of 30 seconds prior to puncturing at -5.0 psigusing two different vacuum fixtures. The first fixture was a 15 mmdiameter vacuum fixture (i.e., a hollow cylindrical tube) used without anet strung across the opening of the tube. The second fixture was a 15mm diameter vacuum fixture (i.e., a hollow cylindrical tube) used with anet strung across the opening of the tube. The net prevented skin frombeing raised up into the vacuum fixture. The same vacuum fixture usedprior to puncturing was applied for a period of 30 seconds afterpuncturing. The fixture was held level with the plane of the skin. Fourpunctures were carried out per person per condition (without net, withnet). Accordingly, it can be seen that a total of 32 runs were carriedout. Blood was collected into capillary tubes. The amount of bloodcollected was determined by measuring the length of blood in the tubes.The percentage of collections in which the volume of blood collectedexceeded 1.0 μL was calculated. Sensation of pain was also recorded.Blood collection results are set forth in TABLE IV.

                  TABLE IV                                                        ______________________________________                                                                  Percent of samples                                  Net        Average volume of blood                                                                      having >1 μL of blood                            across nosepiece                                                                         sample collected (μL)                                                                     collected                                           ______________________________________                                        No         5.2            87                                                  Yes        0.6            19                                                  ______________________________________                                    

The pain results were as follows:

pain of 1=94%

pain of 2=6%

pain of 3=0%

The magnitude of the difference in volume of blood collected and successrates (i.e., percent of samples having >1 μL of blood collected) betweenthe condition of stretching the skin in combination with a vacuum andthe condition of not stretching the skin in combination with a vacuumwas unexpected. The pain scores were low. This example demonstrates thatthe combination of skin stretching and applied vacuum significantlyincreased the volume of blood extracted.

Example 5

This example illustrates the effect the area of the extraction site hason blood collected.

Each of four people had his forearm (dorsal forearm, middle of forearm)punctured at 32 different positions on the forearm with a "BDULTRA-FINE" lancet in a modified "MEDISENSE" lancet assembly. The"MEDISENSE" lancet assembly had been modified with a more powerfulspring and a port had been added.

Vacuum was applied for less than five seconds prior to puncturing. Theforearm was punctured under a vacuum of either -5.0 psig or -7.5 psig.The vacuum applied was maintained for 30 seconds after puncturing. Thediameter of the pipette tip used to apply vacuum after puncturing wasvaried, with diameter of 4, 6, 8, and 10 mm being used. Four puncturesper condition (diameter, vacuum level) were carried out per person.Accordingly, it can be seen that a total of 128 runs were carried out.Blood was collected into capillary tubes. The amount of blood collectedwas determined by measuring the length of blood in the tubes. Thepercentage of collections in which the volume of blood collectedexceeded 1.0 μL was calculated. Sensation of pain was also recorded.Blood collection results are set forth in TABLE VA and VB.

                  TABLE VA                                                        ______________________________________                                        vacuum level = -5.0 psig                                                                               Percent of samples                                   Vacuum    Average volume of blood                                                                      having >1  μL of blood                            diameter (mm)                                                                           sample collected (μL)                                                                     collected                                            ______________________________________                                        4         0.3            0                                                    6         1.7            69                                                   8         3.4            94                                                   10        4.1            100                                                  ______________________________________                                    

                  TABLE VB                                                        ______________________________________                                        vacuum level = -7.5 psig                                                                               Percent of samples                                   Vacuum    Average volume of blood                                                                      having >1  μL of blood                            diameter (mm)                                                                           sample collected (μL)                                                                     collected                                            ______________________________________                                        4         0.8            25                                                   6         3.1            94                                                   8         3.4            81                                                   10        6.3            94                                                   ______________________________________                                    

The pain results were as follows:

pain of 1=89%

pain of 2=10%

pain of 3=1%

The volume of blood collected and success rates (i.e., percent ofsamples having >1 μL of blood collected) were found to vary directlywith the area of skin raised up into the device by the vacuum. A muchgreater volume of skin was raised up into the larger diameter pipettetip than into the smaller diameter pipette tips.

Example 6

This example illustrates that a plastic multiple point lancet can beused with heat and vacuum to collect a useful amount of blood.

Each of four people had his forearm (dorsal forearm, middle of forearm)punctured sixteen times (at sixteen different positions on the forearm)with a Greer Derma PIK® System for allergy testing (Greer Laboratories,Inc., Lenoir, N.C. 28645) modified to fit into a "MEDISENSE" lancetassembly. Pre-heating was carried out at approximately 40° C. and 45° C.for 15 and 60 seconds prior to puncturing prior to puncturing. Fourpunctures were carried out per condition (temperature, time) per person.Accordingly, it can be seen that a total of 64 runs were carried out.

Heat was applied with a heating block, which comprised an aluminum blockhaving one face covered with a "KAPTON" film heater element controlledby an "OMEGA" DP 41 temperature controller using a T-type thermocoupleand the opposite face in contact with the larger base of a frustum of acone made of copper. The larger base of the frustum had a diameter of0.50 in. The height of the frustum was 0.50 in. The smaller base of thefrustum had a diameter of 0.35 in. The smaller base had a cylindricalopening having a diameter of 0.125 in. The cylindrical opening had acommon axis with the frustum. The cylindrical opening reduced theheating surface of the copper frustum. Vacuum (-5.0 psig) was appliedfor a period of 30 seconds after puncturing. The vacuum in contact withthe skin was formed by a pipette tip having a diameter of 8 mm. Thepipette tip was held level with the plane of the skin. Blood wascollected into capillary tubes. The amount of blood collected wasdetermined by measuring the length of blood in the tubes. The percentageof collections in which the volume of blood collected exceeded 1.0 μLwas calculated. Sensation of pain was also recorded. Blood collectionresults are set forth in TABLE VI.

                  TABLE VI                                                        ______________________________________                                        Temperature              Percent of samples                                   (° C.)/Time                                                                     Average volume of blood                                                                       having >1  (μL) of blood                          (seconds)                                                                              sample collected (μL)                                                                      collected                                            ______________________________________                                        40/15    2.4             31                                                   40/60    2.6             50                                                   45/15    2.3             56                                                   45/60    5.2             81                                                   ______________________________________                                    

The pain results were as follows:

pain of 1=100%

pain of 2=0%

pain of 3=0%

This example demonstrates that a blood extraction process employing amulti-point plastic lancet, pre-piercing heating, skin stretching, andpost-piercing vacuum can extract at least 1 μL of blood at least 5% ofthe time.

Example 7

A prototype of the lancing assembly of this invention was tested invitro for kinematic performance, using a "BD ULTRA-FINE" brand lancetand a solenoid valve supplied by the Lee Co, Model No. LHDA0511111H.Design parameters of the prototype are listed below. The definitions ofthese parameters were previously set forth.

    ______________________________________                                        A            =30.7 mm.sup.2 (diameter = 6.25 mm)                              M            =1.2 grams                                                       S            =10 mm                                                           X.sub.p      =n/a                                                             K.sub.s      =19.5 N/m                                                        X.sub.s      =8.7 mm                                                          C.sub.v      =0.015                                                           Dt.sub.v     =0.7 msec                                                        V.sub.c      =0.01 cc                                                         V.sub.v      =5 cc                                                            P.sub.a      =14.7 psia (=0 psig)                                             P.sub.v      =6.7 psia (=-8.0 psig)                                           T.sub.a      =25° C.                                                   Ff           =0.13 N-0.18 N                                                   ______________________________________                                    

This configuration resulted in good lancing results when tested on humansubjects. The measured lancet speed at the end of the stroke was 2.7m/sec.

Example 8

Glucose detectors in the form of multiple-layer elements comprising thefollowing layers, from top to bottom, were prepared:

(1) meter-contactable layer

(2) detecting layer

(3) overcoat layer

(4) blood-transporting layer

(5) covering layer

The arrangement of the layers is shown schematically in FIGS. 11A and11B of copending application entitled METHOD AND APPARATUS FOR OBTAININGBLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005. US.P2, filed onevendate herewith, the entirety of which is incorporated herein byreference. However, the overcoat layer is substantially coplanar withthe blood-transporting layer as shown in FIG. 18 of Attorney's DocketNo. 6005. US.P2.

The multiple-layer element was placed in an apparatus similar to thatshown in FIG. 2. A vacuum of -7.5 psig was applied. The apparatus wasplaced in contact with the forearm of a volunteer. The skin of theforearm was stretched and it raised up into the nosepiece, where it camenear to or into contact with the covering layer of the multiple-layerelement. After the vacuum had been applied for five seconds, the lancetwas fired into the skin by means of a pneumatic lancet assembly of thetype illustrated in FIGS. 11 and 12. The lancet passed through theopenings in the meter-contactable layer and in the covering layer. Thelancet was retracted and blood began to emerge from the forearm of thevolunteer. The vacuum aided in the extraction of blood until the bloodreached the blood-transporting layer. The blood was then transportedalong the blood-transporting layer until it reached the detecting layerof the multiple-layer element. When the blood reached the detectinglayer of the multiple-layer element, an electrical current wasgenerated. This current was used to determine when to release thevacuum.

Eight volunteers were tested as described in the previous paragraph. Thetime required for the multiple-layer element to fill after the lancingoperation was recorded. The type of multiple-layer element used in thisexample had one opening in the meter-contactable layer, as described inExample 8 and shown in FIGS. 11A, 11B, 15, and 18 of Attorney's DocketNo. 6005. US.P2. The multiple-layer element was considered to be filledwhen a current of 1.5 μA was generated. The vacuum was then released andthe integrated current (i.e., charge) was recorded. The lancingprocedure and data collection were repeated four times per volunteer.Blood filled the multiple-layer element in less than 40 seconds for 97%of the tests. The average time required to fill the multiple-layerelement was 15.9 seconds.

Example 9

Glucose detectors in the form of multiple-layer elements comprising thefollowing layers, from top to bottom, were prepared:

(1) meter-contactable layer

(2) detecting layer

(3) overcoat layer

(4) blood-transporting layer

(5) covering layer

The arrangement of the layers is shown schematically in FIGS. 11A and11B of copending application entitled METHOD AND APPARATUS FOR OBTAININGBLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005. US.P2, filed onevendate herewith, the entirety of which is incorporated herein byreference. However, the overcoat layer is substantially coplanar withthe blood-transporting layer as shown in FIG. 18 of Attorney's DocketNo. 6005. US.P2.

The multiple-layer element was placed in an apparatus similar to thatshown in FIG. 2. A vacuum of -7.5 psig was applied. The apparatus wasplaced in contact with the forearm of a volunteer. The skin of theforearm was stretched and it raised up into the nosepiece, where it camenear or into contact with the covering layer of the multiple-layerelement. After the vacuum had been applied for five seconds, the lancetwas fired into the skin by means of a pneumatic lancet assembly of thetype illustrated in FIGS. 16 and 17.

The lancet passed through openings in the meter-contactable layer andthe covering layer of the multiple-layer element. The lancet wasretracted and blood began to emerge from the forearm of the volunteer.As quickly as possible, the multiple-layer element was slidapproximately 2 mm in the direction away from the electrical contacts.This type of movement is more fully described in copending applicationentitled METHOD AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS,Attorney's Docket No. 6005. US.P4, filed on evendate herewith, theentirety of which is incorporated herein by reference. The vacuum aidedin the extraction of blood until the blood reached theblood-transporting layer. The blood was then transported along theblood-transporting layer until it reached the detecting layer of themultiple-layer element. When the blood reached the detecting layer ofthe multiple-layer element, an electrical current was generated. Thiscurrent was used to determine when to release the vacuum.

Nine non-diabetic volunteers were tested as described in the previousparagraph. Each volunteer was tested with two types of multiple-layerelement. One type of multiple-layer element had two openings in themeter-contactable layer, as described in Example 9 and shown in FIG. 16Aof Attorney's Docket No. 6005. US.P2. The other type of multiple-layerelement had one opening in the meter-contactable layer, as described inExample 9 and shown in FIG. 16B of Attorney's Docket No. 6005. US.P2.The time required for the multiple-layer element to fill after thelancing operation was recorded. The multiple-layer element wasconsidered to be filled when a current of 1.5 μA was generated. Thevacuum was then released. The lancing procedure and data collection wererepeated eight times per volunteer per element. Blood filled themultiple-layer element having one opening in the meter-contactable layerin less than 40 seconds for 95% of the tests. Blood filled themultiple-layer element having two openings in the meter-contactablelayer in less than 40 seconds for 96% of the tests. The average timerequired to fill the multiple-layer element having two openings in themeter-contactable layer was 14 seconds. The average time required tofill the multiple-layer element having one opening in themeter-contactable layer was 11 seconds.

Example 10

FIG. 20 illustrates a preferred installation of the lancing assemblyshown in FIGS. 11 and 12 inside a prototype of an embodiment of theblood collecting apparatus of this invention. Additional details of thisembodiment can be found in copending application entitled METHOD ANDAPPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's DocketNo. 6005. US.P4, filed on evendate herewith, the entirety of which isincorporated herein by reference. The lancing assembly 1200, shown inits retracted pre-thrust position, has been fitted with a standardlancet assembly 1202 and a three-way solenoid valve 1204. The cap 1206of the lancing assembly 1200 is fitted into the partition 1207 of theapparatus 1000, thereby forming an effective seal against the partition1207. The apparatus 1000 comprises a housing 1002, which comprises adoor portion 1002a and a body portion 1002b. The exit port 1208 of thelancing assembly 1200 is connected to a vacuum pump 1210 by means of apassageway 1212, such as, for example, a connecting tube. The passageway1212 is also connected to a cavity 1213 inside the door portion 1002a ofthe apparatus 1000. In this manner, the vacuum pump 1210 can deliver anequal level of vacuum pressure to the cavity 1213 and to the exit port1208. The vacuum pressure inside the cavity 1213 can be maintained at alevel at which the apparatus 1000 operates, because the vacuum pump 1210can draw evacuated air from the cavity 1213 at a rate faster than therate at which ambient air leaks into the cavity 1213 by way of the doorseal 1007, the seal placed against the skin of a patient 1010, and theseal formed between the cap 1206 and the partition 1207 (not shown). Thebody 1002b of the housing 1002 of the apparatus 1000 contains air havinga pressure level equal to the ambient pressure surrounding theapparatus. The level of pressure inside the body 1002b of the housing1002 does not change during operation of the apparatus because the body1002b of the housing 1002 contains a sufficient number of openings (notshown) that communicate with the surrounding ambient air. The air insidethe body 1002b of the housing 1002 can enter the lancing assembly 1200through the inlet port 1214 when the solenoid valve 1204 is activated tobegin the lancing step. The difference in air pressure between theambient air inside the body 1002b of the housing 1002 and the evacuatedair inside the cavity 1213 in the door portion 1002a of the housing 1002brings about the differential gas pressure needed to operate the lancingassembly. During the lancing step, the thrusting motion of the lancetassembly 1202 is halted by a lancet stop 1216. The lancet stop 1216 hasan opening (not shown) that allows the lancet 1218 to pass through andpenetrate the skin which is placed against the seal 1010. The lancingassembly in FIG. 20 can thus be used in a manner substantially identicalto that shown in FIGS. 15A, 15B, and 15C.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. An assembly capable of providing an opening in anarea of skin of a patient by means of lancet, comprising:(a) a holderfor holding a lancet assembly; (b) a means for providing sufficientforce to cause said holder to be maintained in a position whereby alancet in said holder would be positioned away from said skin of saidpatient; (c) a means for allowing a gas to provide sufficient force toovercome the force provided by said holder maintaining means, wherebysaid gas causes said holder to be moved to a position whereby a lancetin said holder would be able to pierce said skin of said patient; and(d) a means for reducing level of pressure in said area of said skin ofsaid patient below 0 psig.
 2. The assembly of claim 1, further includinga lancet assembly in said holder.
 3. The assembly of claim 1, whereinmovement of said holder is brought about by means of said gas acting ona piston attached to said holder.
 4. The assembly of claim 3, whereinsaid holder maintaining means (b) is a piston biasing means.
 5. Theassembly of claim 4, wherein said piston biasing means is a spring. 6.An assembly capable of providing an opening in an area of skin of apatient by means of lancet, comprising:(a) a holder for holding a lancetassembly; (b) a means for providing sufficient force to cause saidholder to be maintained in a position whereby a lancet in said holderwould be positioned away from said skin of said patient; and (c) a meansfor allowing a gas to provide sufficient force to overcome the forceprovided by said holder maintaining means, whereby said gas causes saidholder to be moved to a position whereby a lancet in said holder wouldbe able to pierce said skin of said patient, wherein said holdermaintaining means (b) is a piston biasing means, wherein said pistonbiasing means is a bellows.
 7. The assembly of claim 1, wherein saidmeans (c) comprises a piston attached to said holder, said piston beingdisposed in a bore, said bore being capable of being opened to allowsufficient gas at sufficient pressure to enter to move said piston,whereby said holder is moved to said position whereby a lancet in saidholder would be able to pierce the skin of said patient.
 8. An assemblycapable of providing an opening in an area of skin of a patient by meansof lancet, comprising:(a) a holder for holding a lancet assembly; (b) ameans for providing sufficient force to cause said holder to bemaintained in a position whereby a lancet in said holder would bepositioned away from said skin of said patient; and (c) a means forallowing a gas to provide sufficient force to overcome the forceprovided by said holder maintaining means, whereby said gas causes saidholder to be moved to a position whereby a lancet in said holder wouldbe able to pierce said skin of said patient, wherein said means (c)comprises a piston attached to said holder, said piston being disposedin a bore, said bore being capable of being opened to allow sufficientgas at sufficient pressure to enter to move said piston, whereby saidholder is moved to said position whereby a lancet in said holder wouldbe able to pierce said skin of said patient, wherein said means (c)further comprises a valve having a first port, a second port, and athird port, said first port capable of communicating with a source ofgas at a first pressure, said second port capable of communicating withsaid bore, said third port capable of communicating with a source of gasat a second pressure, said second pressure being lower than said firstpressure.
 9. The assembly of claim 7, further including a means forsealing said bore.
 10. The assembly of claim 9, wherein said sealingmeans is an o-ring.
 11. An assembly capable of providing an opening inan area of skin of a patient by means of lancet, comprising:(a) a holderfor holding a lancet assembly; (b) a means for providing sufficientforce to cause said holder to be maintained in a position whereby alancet in said holder would be positioned away from said skin of saidpatient; and (c) a means for allowing a gas to provide sufficient forceto overcome the force provided by said holder maintaining means, wherebysaid gas causes said holder to be moved to a position whereby a lancetin said holder would be able to pierce said skin of said patient,wherein said means (c) comprises a piston attached to said holder, saidpiston being disposed in a bore, said bore being capable of being openedto allow sufficient gas at sufficient pressure to enter to move saidpiston, whereby said holder is moved to said position whereby a lancetin said holder would be able to pierce said skin of said patient, saidassembly further including a means for sealing said bore, wherein saidsealing means is a bellows.
 12. An assembly capable of providing anopening in an area of skin of a patient by means of lancet,comprising:(a) a holder for holding a lancet assembly; (b) a means forproviding sufficient force to cause said holder to be maintained in aposition whereby a lancet in said holder would be positioned away fromsaid skin of said patient; and (c) a means for allowing a gas to providesufficient force to overcome the force provided by said holdermaintaining means, whereby said gas causes said holder to be moved to aposition whereby a lancet in said holder would be able to pierce saidskin of said patient, wherein said means (c) comprises a piston attachedto said holder, said piston being disposed in a bore, said bore beingcapable of being opened to allow sufficient gas at sufficient pressureto enter to move said piston, whereby said holder is moved to saidposition whereby a lancet in said holder would be able to pierce saidskin of said patient, said assembly further including a means forsealing said bore, wherein said sealing means is a diaphragm.
 13. Theassembly of claim 1, further including a piston, attached to saidholder, which piston (1) travels in a first direction in a bore when gasat a first pressure enters said bore and said first pressure exceeds thepressure of gas in said bore prior to said entry of said gas at saidfirst pressure and (2) travels in a second direction in said bore whensaid holder maintaining means (b) overcomes the force of gas acting onsaid piston in said bore.
 14. An assembly capable of holding a lancetassembly for providing an opening in skin of a patient, comprising:(a) ahousing havinga bore having an axis; a valve fitted in a valve manifold;a first port in said valve manifold that allows said valve manifold toallow passage of gas at a first pressure through a first port in saidvalve; a second port in said valve manifold that allows said valvemanifold to allow passage of said gas at said first pressure through asecond port in said valve to enter said bore; a third port in said valvemanifold that allows said valve manifold to allow passage of gas fromsaid bore through a third port in said valve to a location having gas ata second pressure, said first pressure being greater than said secondpressure; (b) a piston disposed in said bore, said piston having aproximal end and a distal end, said proximal end adjacent to said secondport and said distal end including a holder for holding a lancet, saidpiston capable of moving along the axis of said bore; (c) means forbiasing said piston so that said proximal end of said piston is in thefurthest position away from the skin of said patient when said firstport is closed.
 15. The assembly of claim 14, wherein said pistonbiasing means (c) is a spring.
 16. The assembly of claim 14, whereinsaid piston biasing means (c) is a bellows.
 17. The assembly of claim14, wherein said valve is actuated by a solenoid.
 18. The assembly ofclaim 14, further including a means for sealing said bore.
 19. Theassembly of claim 18, wherein said means for sealing said bore is ano-ring.
 20. The assembly of claim 18, wherein said means for sealingsaid bore is a bellows.
 21. The assembly of claim 18, wherein said meansfor sealing said bore is a diaphragm.
 22. A method for forming anopening in an area of skin of a patient in order to obtain blood, saidmethod comprising the steps of:(1) providing a lancing assembly capableof providing an opening in an area of skin of a patient by means oflancet, comprising:(a) a holder for holding a lancet assembly; (b) ameans for providing sufficient force to cause said holder to bemaintained in a position whereby a lancet in said holder would bepositioned away from said skin of said patient; (c) a means for allowinga gas to provide sufficient force to overcome the force provided by saidholder maintaining means, whereby said gas causes said holder to bemoved to a position whereby a lancet in said holder would be able topierce said skin of said patient; (d) a means for reducing level ofpressure in said area of said skin of said patient below 0 psig; and (e)a lancing assembly in said holder, (2) positioning said lancing assemblysufficiently close to said skin of said patient so that a lancet in saidlancet assembly can pierce said skin of said patient; (3) reducing levelof pressure in said area of said skin of said patient below 0 psig; and(4) causing said means (c) to allow a gas to provide sufficient force toovercome the force provided by said holder maintaining means, so thatsaid holder is moved to a position whereby said lancet in said lancetassembly pierces said skin of said patient; and (5) causing said lancetto be retracted from said skin of said patient.